SIMH/HP 2100 RELEASE NOTES ================================ J. David Bryan Last update: 2020-11-07 This file documents the release history of the simulator for the Hewlett-Packard 2114, 2115, 2116, 2100, 1000-M, 1000-E, and 1000-F machines. The home page for the HP simulators is: http://simh.trailing-edge.com/hp/ An HP 2100 "release" is made when one or more major changes have been incorporated. Each release is documented below and describes the changes (new features and corrected errors) that have occurred since the prior release. A revised "HP 2100 Simulator User's Guide" accompanies every release where user-visible changes were made. A "release update" is made to fix minor errors that do not affect normal user operation. Examples of updates might be expansion or correction of source file comments, minor algorithm improvements, or rewording of error messages. Updates are not documented here, although every change is reported in the change logs that appear at the beginning of all HP 2100 source files. The HP simulators were previously associated with the "SIMH 4.0" project here: https://github.com/simh/simh ...but are no longer. Any simulator reporting itself as "V4.x" is not authorized and not supported by your HP maintainer. Regression testing with the original HP diagnostics suites is performed only on the simulators available from the trailing-edge site. See the notes below for more information on this transition. =============================== Reporting Bugs in the Simulator =============================== If you find a bug in the HP 2100 simulator, please report it directly to your HP maintainer at the address shown at the top of these notes. Please attach a console log that shows the simulator version and contains a reproducible test case that illustrates the problem. See the SET CONSOLE LOG command in the "Console Options" section of the "SIMH Users' Guide" for details on how to enable logging and the SHOW VERSION command in the "Displaying Parameters and Status" section. ============================= The 4.x to 3.x SCP Transition ============================= Internally, a SIMH simulator consists of a "front end," designated the Simulator Control Program (SCP), and a "back end" that provides the machine-specific personality. SCP provides the simulator prompt, console commands such as ATTACH and RUN, and common library modules for magnetic tape, terminal, and other device support. SCP manages command file execution, cooperates with the back end to configure the CPU and I/O devices, and relinquishes control to the back end to execute machine instructions when a RUN, GO, or CONTINUE command is entered. The SIMH project was created and led by Bob Supnik through SCP version 3.9. Mark Pizzolato then assumed stewardship and substantially extended SCP for version 4.0. Recently, Bob has produced SCP version 3.10, which adopts some, but not all, of the new features provided with version 4.0. It also has a markedly simpler internal structure compared to 4.0. The HP 2100 simulator had been migrated from SCP 3.9 to 4.0, but the rapid development cycle and greatly increased complexity introduced a number of errors and incompatibilities that made it very difficult to ensure stable HP simulator operation. Regression testing became problematic; often the SCP would change between simulator testing and code release. This has led to an untenable support situation. Therefore, starting with Release 29, the simulator has been retargeted to SCP 3.10 and its successors, which will be used for all future releases. This does not affect machine execution, i.e., once a RUN or GO command is given, but it does have consequences for user-written command files, as SCP 3.10 does not implement all of the new-for-4.0 commands. The HP simulators provide a superset of the SCP 3.10 commands. These are documented in the "SIMH Users' Guide Supplement" that is provided in PDF format in the "doc" subdirectory of the distribution archive. Those with existing user-written command files should consult this document for the ramifications of the SCP transition. =================== General Information =================== The simulator passes the HP 24396 offline diagnostic suite with some expected failures due to unimplemented features. For example, the disc diagnostic error-correction logic tests and the tape diagnostic CRCC and LRCC tests fail, as these features are not supported. However, all features that are required for operation of the supported HP operating systems pass their respective diagnostic tests. See the accompanying "hp2100_diag.txt" file for details. The simulator has been tested with the following operating systems: - SIO, BCS, and MTS. - 2000E, 2000F, and 2000 Access Time-Shared BASIC. - DOS, DOS-M, and DOS-III. - RTE, RTE-B, RTE-C, RTE-II, RTE-III, RTE-IV, RTE-IVB, and RTE-6/VM. The user's manual for the simulator is provided in PDF format in the "doc" subdirectory of the distribution archive. For those intending to run 2000F or 2000/Access Time-Shared BASIC, a monograph entitled "Running HP 2000 Time-Shared BASIC on SIMH" is available from the "Documentation" section of the simulator site listed above. It discusses the requirements for successful TSB startup and operation and the issues involved in synchronizing the dual-CPU simulation setup required by TSB. TSB has run successfully on SIMH for many years, but the advent of multi-core host machines has increased the difficulty in getting the two SIMH instances to coordinate properly. The paper presents some configuration guidelines that improve the probability of successfully running TSB. Another paper available from the simulator site is entitled "The Evolution of the HP 21xx/1000 I/O Simulation" and describes the several I/O simulation designs that have been employed in the simulator as it has evolved to accommodate the widening range of I/O device interfaces. It also describes in detail the current design and its tradeoffs, and serves as a tutorial for those intending to write their own HP interface simulations. ----------------------- Compiling the Simulator ----------------------- Compilation instructions are documented in Section 1 of the "SIMH Users' Guide Supplement" that is provided in PDF format in the "doc" subdirectory of the distribution archive. ------------------ Available Software ------------------ Ready-to-run software kits for several of the HP 21xx/1000 operating systems are available from the "Software Kits" section of the simulator site listed above. Each kit contains a bootable disc or tape image and associated command files that automate the system startup process. Command files to perform new system generations are also included. Refer to the site for details. The Computer History Museum has graciously arranged with HP to offer the HP 1000 Software Collection with a sublicense for non-commercial use by private individuals. The Collection is hosted by Bitsavers at: http://www.bitsavers.org/bits/HP/HP_1000_software_collection/ QCTerm, a free HP 700 terminal emulator for Microsoft Windows, is available from the HP Computer Museum at: http://www.hpmuseum.net/display_item.php?sw=585 Use of an HP terminal via a serial port or an HP terminal emulator via Telnet enables more advanced screen editing features of the RTE operating systems. Generic Telnet clients generally will work, albeit with reduced functionality. Manuals describing the operation of HP software are available from Bitsavers at: http://www.bitsavers.org/pdf/hp/1000/ http://www.bitsavers.org/pdf/hp/2000TSB/ http://www.bitsavers.org/pdf/hp/21xx/ ...and from the HP Computer Museum at: http://www.hpmuseum.net/collection_document.php#CS ---------------- Year 2000 Issues ---------------- RTE-6/VM Revision 6200 is Y2K compliant, except for the READR and SAVER programs. The errors are cosmetic only. RTE-IVB Revision 5010 is not Y2K compliant. All of the failures are in subsystems; the operating itself (time-of-day clock) accommodates dates through 2059. All of the errors are cosmetic. Typically, punctuation characters appear in the years, e.g., "19:0" for 2000. All other HP operating systems are not Y2K compliant. For these, the system time should be set to a corresponding year in the 20th century. Refer to the "Variable Substitution" section of the "SIMH Users' Guide Supplement" for details on using the %DATE_RRRR% and %DATE_RR% substitution variables on non-Y2K-compliant systems. ----------------------------- Bugs in RTE-IVB Revision 5010 ----------------------------- Testing during simulator development revealed the presence of a bug in RTE-IVB Revision 5010: - The $BALC module in the system library has a bug that causes memory corruption. This module is used by the ACCTS program and manifests itself by printing gibberish after the "PLEASE LOG ON:" prompt. Specifically, the internal MXEV routine performs a cross-store indirect via a location in Table Area II (XSA $MAXI+0,I). This fails because the indirect chain is resolved in the user map, but TA II is not present in the user map of large-background programs, such as ACCTS. Therefore, the location in the user map corresponding to $MAXI in the system map is used as the pointer to the location to store. A workaround is to load the ACCTS program as a regular background program instead of as a large background program. Regular background programs include Table Area II in the user map. Note that ACCTS requires SSGA access, so use "OP,BGSS" for online loading or specify "ACCTS,19,90" in the Parameter Input Phase of a system generation. ====================== Release 30, 2020-11-07 ====================== This release of the HP 2100 simulator adds the following features: - A new concurrent-mode FLUSH command has been added to flush terminal logs and attached device files that otherwise would be flushed only when the simulator is stopped. This allows external examination of these files while the simulator continues to run. - Terminal multiplexer line logs are now flushed each time the simulator stops. Prior to this, closing and then reopening a line log was the only way to post buffered writes to disc. - The -N (new file) option has been added to the SET BACI LOG, SET MPX LOG, and SET MUXL LOG commands to create new, blank log files. Without the option, the commands will append to existing log files. - The HP 12972C 8-channel terminal multiplexer (MPX) and 12920A 16-channel terminal multiplexer (MUX) now allow channels to be omitted from the connection order. For example, a SET MPX LINEORDER=0-3 command permits connections to channels 0 through 3. Additional Telnet connection attempts will be rejected with an "All connections busy" message, and attempting to attach a serial port to a line not in the connection order will be rejected with a "Unit not attachable" message. - A new INTERLOCK option has been added to the IPL device. This provides a more precise way of synchronizing the two simulator processes running the HP 2000 Time-Shared BASIC operating system. Entering a SET IPL INTERLOCK= command restricts each process to executing machine instructions before performing a rendezvous with the other process. In this way, both processes remain in approximate lock-step, which substantially improves system startup reliability, even when one process is preempted during initialization by the host operating system. An associated SHOW IPL INTERLOCK command displays the current interlock value. - The IPL device now works on FreeBSD and Cygwin host platforms, as well as the Windows and Linux platforms that were previously supported. - A new -E switch has been added to the ATTACH IPL command. This enables falling back to timed waits if the host platform does not support the synchronization routines necessary for the SET IPL WAIT and SET IPL SIGNAL commands. - The CMD trace option for the IPL device now decodes and reports all TSB commands that pass between the System Processor and the I/O Processor. - The PSERV and STATE trace options have been added to the IPLO device. Enabling the PSERV option traces the periodic calls to the new process synchronizer. Enabling the STATE option traces calls to the host platform event routines, as well as internal synchronizer states during rendezvous. -------------------- Implementation Notes -------------------- - The terminal multiplexer LINEORDER option now omits unspecified lines from the connection order. Prior versions appended unspecified lines to the end of the specified order. To obtain the prior behavior, append the keyword ALL as the last parameter to the connection order list. - New releases of the HP 2000F and 2000 Access software kits use the SET IPL INTERLOCK command instead of the prior SET IPL WAIT/SIGNAL commands to synchronize the two simulator instances and provide more reliable system startup under a wider variety of host system conditions. - The 2000 Access software kit now includes a command file to run the program that converts files between Access and 2000 C/F systems. - The "Running HP 2000 Time-Shared BASIC on SIMH" monograph has been extensively revised to cover the application of the new SET IPL INTERLOCK command to the TSB startup command files. - The previous method of sleeping for a few milliseconds during 2000 Access startup to avoid IOP initialization errors is no longer required when the new IPL interlock is used. The capability has been retained, however, and will be used if the host platform does not support synchronization events. - The size of the shared memory area that simulates the processor interconnection cables of the IPL device has been changed. On Linux and macOS systems, this area is implemented by a file named "HP 2100-MEM-", where is he code number supplied to the ATTACH IPL command. The file is located in the "/dev/shm" directory. If the file is present, it must be removed before running the simulator, or a "File open error" will result when an ATTACH IPL is attempted. The new release of the simulator removes the file automatically when a DETACH IPL is performed, so manual removal must be done only once. ---------- Bugs Fixed ---------- 1. PROBLEM: Breakpoint actions after an included true IF are discarded. VERSION: Release 29. OBSERVATION: If a breakpoint has actions that include an IF command followed by additional actions, and the IF command evaluates to TRUE, then the IF actions executed, but the remaining breakpoint actions are discarded. For example: sim> set environment X=0 sim> break 10 ; if "%X%" == "0" echo X is 0 ; echo Done sim> go One would expect to see: Breakpoint, P: 00010 (NOP) sim> if "0" == "0" echo X is 0 sim> echo X is 0 X is 0 sim> echo Done Done sim> Instead, only the first ECHO is performed. The second one is discarded. However, execution is correct if the IF condition is false: sim> set environment X=1 sim> break 10 ; if "%X%" == "0" echo X is 0 ; echo Done sim> go Breakpoint, P: 00010 (NOP) sim> if "1" == "0" echo X is 0 sim> echo Done Done sim> CAUSE: IF actions are executed by setting the breakpoint action pointer to the action list and returning to the command loop. While the IF command is executing, the pointer is pointing at the "echo Done" part of the breakpoint action list. However, if the IF condition is true, the pointer is changed to point at the "echo X is 0" command, and the remaining breakpoint actions are lost. RESOLUTION: Modify "if_cmd" (sim_extension.c) to append the remaining breakpoint actions to the actions specified by the IF command, so that the former are not lost. STATUS: Fixed in Release 30. 2. PROBLEM: Linking with recent compilers results in duplicate symbol errors. VERSION: Releases 29. OBSERVATION: If the simulator is compiled with a recent compiler version, the link step fails with duplicate symbol errors. The symbols reported are "sim_vm_release", "vm_sim_vm_init", "vm_console_input_unit", and "vm_console_output_unit". CAUSE: The VM hook extension mechanism is implemented with "tentative definitions" of the hook variables. The C standard says: "If a translation unit contains one or more tentative definitions for an identifier, and the translation unit contains no external definition for that identifier, then the behavior is exactly as if the translation unit contains a file scope declaration of that identifier, with the composite type as of the end of the translation unit, with an initializer equal to 0." This behavior is such that if no module contains a definition with an initializer, the hook will have a zero value. However, if a module contains a definition with an initializer, the hook is assigned that value. This allows hooks to be set without changing the hook's tentative definition simply by including a VM module that declares it with an initializer. This mechanism relies on the linker to resolve the multiple definitions of a given hook to a single reference. For this to occur, the compiler must mark tentative definitions as "common" allocations, e.g., with the "-fcommon" option to gcc. Traditionally, gcc (and clang, etc.) defaults to common allocations for tentative definitions. However, the gcc manual claims that, "This behavior is not required by ISO C, and on some targets may carry a speed or code size penalty on variable references." Newer versions (starting with gcc 10) default to data allocations instead ("-fno-common"), and multiple tentative definitions now result in duplicate symbol errors rather than merged accesses. RESOLUTION: Modify sim_extension.h to declare "vm_sim_vm_init" only if the USE_VM_INIT symbol is defined. Modify "ex_initialize" (sim_extension.c) to remove the tentative definition and to make the external "vm_sim_vm_init" call conditional on USE_VM_INIT. Modify "one_time_init" (hp2100_sys.c) to set the "sim_vm_release" hook directly. Modify "tty_reset" (hp2100_tty.c) to set the console unit hooks directly. This removes all tentative definitions from the simulators. STATUS: Fixed in Releases 30. 3. PROBLEM: Trace output to stdout on Unix results in stair-step output. VERSION: Release 29. OBSERVATION: Directing the trace output to "stdout" on a Unix system results in lines stair-stepping across the screen. For example: sim> set console debug=stdout sim> set cpu debug=instr sim> step 2 ...produces this output: >>CPU instr: - 0000 00000 000000 NOP >>CPU instr: - 0000 00001 000000 NOP CAUSE: Trace statements are output with LF ('\n') line ends and depend on host-system translation to the proper line-end convention when the lines are written to the trace log. However, while the simulator is executing instructions, the console is placed in "raw" mode so that output translation, which would interfere with the output from the target operating system, is not done. As there are no carriage returns in the trace output stream when writing to stdout, the console cursor simply drops in place to the next line, so that each line begins at the same column where the previous line ended. RESOLUTION: Modify "hp_trace" (hp2100_sys.c) to convert a terminating LF to a CR LF sequence if output is to stdout. Also modify "sim_instr" (hp2100_cpu.c) to add CR characters to the stdout stream where line termination is done explicitly. STATUS: Fixed in Release 30. 4. PROBLEM: The trace line for an I/O error simulation stop is incomplete. VERSION: Release 29. OBSERVATION: With simulation stops on I/O errors enabled, a CPU trace correctly records the stop, but the stop description is incomplete. For example: sim> set ipl enabled sim> attach -s ipl 1 sim> set cpu stop=ioerr sim> set cpu debug=instr sim> set console debug=stdout sim> go ...produces trace output that ends with: >>CPU instr: - 0000 00061 000000 simulation stop: Cable not connected to ...while the simulation console reports the full message, "Cable not connected to the IPLI device." CAUSE: The trace statement printer for the stop calls "sim_error_text" to obtain the description of the stop status, but that routine does not handle VM-specific additions. Upon returning to SCP, the "run_cmd" routine prints the "sim_error_text" but then calls a VM-specified "sim_vm_fprint_stopped" routine to handle additions to VM stops. RESOLUTION: Modify "sim_instr" (hp2100_cpu.c) to call the VM-specific simulation stop handler via the "sim_vm_fprint_stopped" hook if an I/O error stop occurred. STATUS: Fixed in Release 30. 5. PROBLEM: ATTACH/DETACH MUXL succeeds but should not. VERSION: Release 29. OBSERVATION: The HP 12920A multiplexer simulator defines two devices: the MUX device that contains the polling unit, and the MUXL device that contains the terminal line units. The poll unit is attached with the: ATTACH MUX ...command. Line units are attached to serial ports with the: ATTACH MUXL ...command. These behave as expected. However, the: ATTACH MUXL ...command succeeds but attaches the port to the MUX device. This is incorrect and should be prohibited. CAUSE: The "muxl_attach" routine passes a poll unit pointer to the "tmxr_attach_unit" routine. The latter routine attaches the poll unit instead of the passed line unit when a device is referenced. However, the poll unit belongs to a different device, and so the mux line routine attaches the port to the mux poll device. RESOLUTION: Modify "muxl_attach" and "muxl_detach" (hp2100_mux.c) to pass NULL for the poll unit in the "tmxr_attach_unit" calls. Modify the "ex_tmxr_attach_unit" and "ex_tmxr_detach_unit" routines (sim_extension.c) to reject the call if a device was referenced and a NULL poll unit pointer was passed. STATUS: Fixed in Release 30. ====================== Release 29, 2020-02-15 ====================== This release of the HP 2100 simulator adds the following features: - A new CONCURRENT option has been added to the SET CONSOLE command. Entering CTRL+E with concurrent mode enabled allows the simulator to continue to run while presenting an "scp>" prompt for command entry. This permits SCP commands, such as an ATTACH of a magnetic tape image, to be performed without causing the simulated system clock to lose time and without disturbing command file execution. Concurrent mode is enabled by default. If the prior mode where CTRL+E stops the simulator is desired, a SET CONSOLE NOCONCURRENT command may be placed in the "simh.ini" global initialization file that is read automatically at startup. See the "SIMH Users' Guide Supplement" for details. - The 12731A Memory Expansion Module has been separated from the CPU simulator and assigned to its own device ("MEM"). The MEM registers are now displayed and altered with the EXAMINE MEM and DEPOSIT MEM commands and have been renamed, with the map registers separated into the four functional sets. Enabling and disabling the device is performed indirectly by the SET CPU DMS and SET CPU NODMS firmware-installation commands, rather than by the typical SET MEM ENABLED/DISABLED commands. The CPU feature table in Section 3.1 of the HP2100 User's Guide has been corrected to show that the MEM is an option for the 1000 M/E/F-Series machines, and 1000 systems without memory expansion may be simulated by disabling the DMS instruction set. - Two instances of the 12566B Microcircuit Interface have been added; the device designations are MC1 and MC2. These devices simulate only the interface cards and do not have attached peripherals. They are intended as interrupt and data loopback targets for several HP diagnostic programs and, as such, are disabled by default. - An internal "Keyboard Poll" unit has been added to coordinate keyboard input polling. This unit will be visible in the SHOW QUEUE display. - The TTY device may now be disabled, as its input poll coordination responsibilities have been transferred to the internal keyboard poll unit. This permits correct I/O configuration for systems that do not use a keyboard device (e.g., the I/O Processor in an HP 2000 Time-Shared BASIC system) or for RTE systems that use the BACI as the system console device. Previously, the TTY device would have remained enabled but been assigned a high select code "out of the way" of the correctly configured set of I/O devices. - A new SHOW CPU IOCAGE command has been added to display the set of I/O device interfaces currently installed in the CPU card cage. The devices appear in select code order, beginning with select code 10 and ending with the last occupied select code. This makes checking select code assignments and identifying conflicts much easier than using the SHOW DEVICES command. - The SHOW CPU ROMS command has been extended to add descriptions of the bootstrap loader ROMs installed in HP 1000 CPUs. - The list of the simulated devices displayed by the SHOW DEVICES command has been rearranged to this order: CPU, CPU devices, and I/O devices alphabetically. The prior order was essentially random, making it difficult to locate specific devices. - New SET REALTIME and SET FASTTIME commands have been added to the TTY, PTR, and PTP devices. The optimized timing values used may be altered via the corresponding register interfaces. - The SET PTR DIAGNOSTIC command has been enhanced to provide a second diagnostic mode. If a paper tape image file is not attached, then the new mode simulates the installation of a loopback connector in place of the reader cable, permitting the General Purpose Register Diagnostic to test the interface. If a file is attached, then the existing mode converts the attached paper tape image into a continuous loop by logically joining the ends of the tape, which is needed by the High-Speed Tape Reader/Punch Diagnostic. - The new SET PTR REWIND command repositions the attached tape image to the beginning, so that the tape may be re-read. This is helpful, for instance, when re-running and specifying different output options to a program that takes its input from the paper tape reader. - The new SET PTP DIAGNOSTIC command installs a loopback connector in place of the paper tape punch cable to run the General Purpose Register Diagnostic on the interface. The new SET PTP PUNCH command reinstalls the punch cable and restores normal punch operation. - Configurable debug tracing has been added to the TTY, PTR, and PTP devices. - All I/O devices that had not supported debug tracing previously now provide an IOBUS option to trace data and signals sent and received across the I/O backplane bus. All peripheral devices now support at least minimal tracing. -------------------- Implementation Notes -------------------- - The change from SCP 4.0 to 3.x may affect user-written command files. Be sure to review Section 3, "SCP 4.x-to-3.x Conversion," of the "SIMH Users' Guide Supplement." - The DO command now executes more quietly by default. Specifically, the "Breakpoint" and "Step expired" messages that normally result from BREAK, GO UNTIL, and STEP command completions are suppressed, as are the informational messages from ATTACH and DETACH, such as "Creating new file." This provides a cleaner console display log when automated prompts and responses are used. Adding the -A switch to the DO invocation will restore the previous noisier behavior. See the "DO Command" section of the Supplement for details. - The SHOW CPU ROMS command is now rejected if the CPU is not a 1000. - The ION and ION_DEFER CPU registers have been renamed to INTSYS and INTEN, respectively, to match the names used in the HP engineering documentation. Note that the sense of INTEN is now reversed: a value of 0 indicates that interrupts are not enabled (i.e., are deferred), while 1 indicates that interrupts are enabled (not deferred). - The TTY KTIME register has been removed. This register was intended to allow the user to set the keyboard polling interval, but it never worked; instead, the keyboard poll rate was (and is) always fixed at 100 Hz. - The TTY TTIME register had been described as the "Time from I/O initiation to interrupt" but it actually sets the optimized (FASTTIME) time for Teletype print/punch operations. - The prior method of rewinding a paper tape by doing DEPOSIT PTR POS 0 does not work if the console is in concurrent mode. Use the new SET PTR REWIND command instead. - The I/O system simulation has been rewritten to model the actual hardware more closely. This has no user-visible impact, except that IOBUS tracing now accurately reflects the hardware I/O bus signals. For example, the PRH and PRL signals now appear in IOBUS traces and show the I/O priority settings. Any user-written device interfaces will have to be changed to use the new I/O structure; the Microcircuit Interface in hp2100_mc.c is a simple example that may be used as a model for the changes needed. - The hp2100_stddev.c source file has been split into hp2100_pt.c (PTR and PTP), hp2100_tty.c (TTY) and hp2100_tbg.c (TBG). - hp2100_cpu.c has been split into hp2100_cpu.c (CPU and I/O), hp2100_mem.c (main memory, MP, and MEM), and hp2100_dma.c (DMA1 and DMA2). A new hp2100_cpu_dmm.h file contains the interface declarations for these three modules. - hp2100_fp.c and hp2100_fp1.c have been renamed to hp2100_cpu_fp.c and hp2100_cpu_fpp.c, respectively, and hp2100_fp.h and hp2100_fp1.h have been combined into hp2100_cpu_fp.h. - hp2100_cpu1.h has been retired; its declarations have been moved into hp2100_cpu.h. ---------- Bugs Fixed ---------- 1. PROBLEM: The multiplexer upper data card status trace is incorrect. VERSION: Release 28. OBSERVATION: Tracing status on the upper data card of the 12920A Asynchronous Multiplexer Interface with the SET MUX DEBUG=CSRW command produces incorrect results. For example: >>MUX csrw: Status is channel 17 | seeking | breaklost | receive >>MUX iobus: Returned data 042012 with signals (none) Given the status word 042012 octal, the correct status interpretation is "channel 17 | diagnose | lost | receive". CAUSE: A comma is missing after the "break" string constant in the "upper_status_names" array initializer. This causes the "break" and "lost" strings to be concatenated and used for bit 1. As a result, the "diagnose" and "seeking" strings are used for bits 2 and 14 instead of 3 and 15. RESOLUTION: Modify the "upper_status_names" initializer (hp2100_mux.c) to use the correct set of status names. STATUS: Fixed in Release 29. 2. PROBLEM: Tracing the $MPV instruction prints the wrong mnemonic. VERSION: Release 28. OBSERVATION: Tracing memory protect interrupts on an RTE-6/VM system displays the trap cell instruction mnemonic as "ostst" (the firmware test instruction): >>CPU instr: U 0170 26072 000005 interrupt >>CPU fetch: S 0000 00005 105355 instruction fetch >>CPU instr: S 0000 00005 105355 ostst >>CPU opnd: * **** 26072 105355 entry is for a memory protect violation ...instead of the expected "$MPV" (memory protect violation instruction): >>CPU instr: U 0170 26072 000005 interrupt >>CPU fetch: S 0000 00005 105355 instruction fetch >>CPU instr: S 0000 00005 105355 $MPV >>CPU opnd: * **** 26072 105355 entry is for a memory protect violation CAUSE: The RTE-6/VM OS firmware designates four instruction opcodes as "dual-use." Opcodes 105354-105357 take different actions, depending on whether or not they are executed from a trap cell during an interrupt. The routine that formats these instructions for trace output determines the mnemonic table to use by the address in which the instruction is stored. The address value is also used to communicate to the "fprint_instruction" routine whether or not the value array containing the instruction word(s) has been loaded. For a CPU instruction trace, only the first word of the array is loaded (as part of the instruction fetch), so the address value has an upper bit set to indicate this condition. However, the trap cell check is not masking this bit off, so instructions executing from trap cells are treated as though they are executing from high memory. RESOLUTION: Modify "fprint_cpu" (hp2100_sys.c) to mask the target address before checking the location when printing "dual-use" instructions. STATUS: Fixed in Release 29. 3. PROBLEM: DIAGNOSTIC mode of the 12653A Line Printer Interface is not modeled correctly. VERSION: Release 28. OBSERVATION: The 12653A Line Printer Interface used with the HP 2767A line printer (LPS device) is a modified 12566B Microcircuit Interface. Setting the card for DIAGNOSTIC mode simulates the installation of an HP 1251-0332 diagnostic test (loopback) connector in place of the printer cable and the alteration of the jumper configurations to match those required by the diagnostics that target this interface. When the Direct Memory Access Diagnostic for the 2115/2116 computer (DSN 101105) was first run, Test 17, which tests character unpacking during output, failed. It was originally thought that the 12578A DMA card for the 2115 and 2116 had a one-cycle startup latency that did not exist in the 12607B, 12895A, and 12897B DMA cards for the 2114, 2100, and 1000-series CPUs. This latency was added to the simulation in version 3.7-0, and the diagnostic passed. Sometime later, the schematic for the 12578A card was studied more closely, revealing that the first DMA cycle occurred immediately upon activation when SRQ (Service Request) was already asserted, as it was in the diagnostic, so the latency counter was removed. In its place, the LPS device was modified to change SRQ assertion timing for 211x CPUs. With the loopback connector in place, asserting STC caused the flag to set and SRQ to assert after a delay of one instruction. The 12578A diagnostic required different jumper settings on the 12653A card than were used by the other diagnostics, and it was assumed that this caused the card to assert SRQ after a delay of two instructions. These changes were made in version 3.9-0. A copy of the 12653A interface manual was obtained recently, and studying the schematic revealed that the unusual jumper settings still resulted in SRQ assertion after a one-instruction delay. Restoring the simulation to the correct delay caused diagnostic test 17 to fail again. CAUSE: Timing analysis of the response to DMA cycles on 2115 and 2116 machines shows that the jumper settings employed by the diagnostic suppress setting of the Flag Buffer flip-flop, so no SRQ assertion occurs. The STC and CLF signal assertions that start an I/O operation are coincident and one T-period in duration (200 ns) in all combinations of CPU models and cycle types EXCEPT when asserted for a 211x DMA cycle, where they are two T-periods in duration (400 ns) and CLF lags STC by one T-period. With the DMA diagnostic strapping, the Flag Buffer flip-flop is set by the STC and then cleared by the lagging CLF in the same DMA cycle. This inhibits SRQ, so DMA pauses until the diagnostic can examine the DMA state and then issue a programmed STC/CLF to assert SRQ. This permits test 17 to succeed. RESOLUTION: Create a new 12566B Microcircuit Interface simulator (hp2100_mc.c) to implement the three different strapping behaviors required by the various DMA diagnostics. Simplify "lps_interface" (hp2100_lps.c) to operate in the manner expected by the General Purpose Register Diagnostic when the card is in DIAGNOSTIC mode. STATUS: Fixed in Release 29. 4. PROBLEM: Simulation stops are reported improperly in CPU traces. VERSION: Release 28. OBSERVATION: A simulation stop that occurs while CPU tracing is enabled reports the cause of the stop in the trace log. However, stop reasons specific to the HP simulator are not reported properly. For example, tracing a halt instruction reports "simulation stop: Error 5" instead of "simulation stop: Programmed halt". CAUSE: The "sim_error_text" routine called to obtain the error translation does not return simulator-specific messages. Instead, the routine returns the generic message, "Error ", where is the value of the simulator- specific stop code. RESOLUTION: Modify the simulation stop trace at the end of the instruction postlude in "sim_instr" (hp2100_cpu.c) to call "sim_error_text" for SCP errors and to obtain HP-specific messages from the "sim_stop_messages" array. STATUS: Fixed in Release 29. 5. PROBLEM: RTE-IVB FMGR aborts with a DM error during :DL,2 output. VERSION: Release 28. OBSERVATION: Entering a DL,2 command at the system console begins listing the cartridge but then aborts partway through with this error: DM VIOL = 100377 DM INST = 126313 ABE 0 177777 0 XYO 47252 0 0 DM FMGR 34463 FMGR ABORTED The system generation log shows that address 34463 is within the "CLOSE" subroutine. The violating instruction is a JMP 34313,I that attempts to return from the subroutine. However, the return address is 14054,I (i.e., an indirect pointer) that points to 2000,I that points to 77765,I that is in unmapped memory. This generates a MEM read violation. CAUSE: The subroutine does a JSB .ENTR at entry to obtain the parameters and adjust the return address. As this system has the Fast FORTRAN Processor firmware, the JSB .ENTR is replaced with the .ENTR microcode instruction. A CPU trace shows that a TTY interrupt is generated after the JSB 45,I that calls the subroutine. Because JSB,I disables interrupt recognition, the TTY interrupt is deferred until the next instruction executes. The .ENTR instruction checks for interrupts when resolving the address of each supplied subroutine parameter. Consequently, the deferred TTY interrupt is recognized when the first parameter is resolved, and the .ENTR instruction exits with the P register set so that the instruction will be reexecuted when the TTY interrupt handler exits. However, the return address was updated before the interrupt was recognized, so reexecution updates the return address a second time. This results in an incorrect address, which causes the DM abort when the subroutine attempts to return. RESOLUTION: Modify the .ENTR handler in "cpu_ffp" (hp2100_cpu3.c) to update the return address only if the instruction executes to completion. STATUS: Fixed in Release 29. 6. PROBLEM: The MEM Violation Register is not freezing for a DM error. VERSION: Release 28. OBSERVATION: The value that RTE reports for the Memory Expansion Module's Violation Register during a DM abort does not match the value of the VR obtained by a CPU trace. For example, a trace may show: >>CPU instr: U 0167 34464 000005 interrupt >>CPU reg: - **** ***** ****** MPF 030000, MPV 034463, MES 163454, MEV 100377 ...but then: >>CPU instr: S 0023 47516 101731 RVA >>CPU fetch: S 0023 47517 000040 instruction fetch >>CPU reg: - **** 01454 000000 A 160377, B 034463, X 047252, Y 000000, E o I The value returned by the RVA (Read Violation Register) instruction is not the same as the MEV (MEM Violation) value reported by the trace. Consequently, the value reported by RTE as "DM VIOL =" is wrong. CAUSE: The VR is being changed when it is supposed to be frozen. The MEM schematic shows that the VR clock is inhibited by -MEV until CTL5 goes low and then high again. That is, a MEM violation inhibits the VR clock, which is reenabled when the MP control flip-flop is set (i.e., when MP is reenabled). With CTL5 low, VR should not update. RESOLUTION: Modify "dm_violation" (hp2100_mem.c) to inhibit updating the VR if "mp_mevff" is set or "mp_control" is clear. STATUS: Fixed in Release 29. 7. PROBLEM: DETACH -F LPT will not detach if the print buffer is not empty. VERSION: Release 27. OBSERVATION: The 2607/13/17/18 line printers do not allow the operator to take the printer offline if unprinted characters remain in the print buffer. Instead, the request is deferred until printing completes. The LPT simulator follows this hardware behavior when processing a DETACH LPT command, which simulates running out of paper. If printing is still pending or, for the 2607 only, the paper position is not at the top-of-form, the message "Command not completed" is printed, and the detach is deferred until a print command empties the print buffer and paper movement ceases. A "force" option is provided to detach the printer paper image file immediately, regardless of the printer condition. DETACH -F LPT works if the paper position is not at the TOF. However, it does not work if the print buffer contains unprinted characters; "Command not completed" is displayed instead. Entering RESET LPT followed by DETACH LPT works, but the partial print buffer is discarded rather than flushed to the output file. CAUSE: The "lp_detach" routine sets TOF status if the -F switch is specified, but it does not alter the buffer state. RESOLUTION: Modify "lp_detach" (hp2100_lpt.c) to write a partial line to the output file before detaching when the -F option is specified. STATUS: Fixed in Release 29. 8. PROBLEM: BREAK needs an extra keystroke to stop an HP 2000/Access program. VERSION: 3.7-1 OBSERVATION: According to the "HP 2000/Access BASIC Reference Manual" (HP 22687-90001), pressing the terminal BREAK key halts program execution and prints STOP on the user's terminal. For example, running this program: 10 FOR I=1 TO 10000 20 PRINT I 30 NEXT I 40 END ...and pressing BREAK during execution does stop the program output. However, STOP is not printed until another key (any key) is pressed. Enabling tracing of the multiplexer and the processor interconnect kit shows that the break is being recognized by the IOP, which then notifies the SP by sending a "User abort request" command over the interconnect link. In response, the SP sends "Kill terminal output" and a "User is being aborted" commands to the IOP, followed by a "Process output string" command to print STOP on the user's terminal. The IOP begins the output by sending a SYNC character before the STOP string. When the transmit interrupt occurs after SYNC transmission, the IOP reads the input data register from the mux data card. The data value is 0, which the IOP interprets as another break request. The IOP then sends another "User abort request" command to the SP, which responds with a "Kill terminal output" command, and the cycle repeats. Only when a character is pressed does the input register data change from 0 to a non-zero value, allowing the abort cycle to finish. CAUSE: In hardware, the input data register normally holds the character received from the selected multiplexer channel. This character has been assembled by a shift register that is designated the "accumulator" from the bits arriving on the serial input line. After a send operation, the input data register also stores the value from the accumulator. In this case, however, the value is that contained in the shift register after all of the bits of the output character have been shifted out to the serial output line. As each output character is padded on the left with 1 bits (representing the serial stop bits) to an 11-bit length, if the character length is less than 11, at least one 1-bit will remain in the register. Therefore, when the IOP reads the register during processing of the transmission interrupt, the value will be non-zero, and the IOP will not restart BREAK processing. Under simulation, however, a send operation places the last received character in the input data register instead of the shifted send character. As the last received character was zero (for the BREAK key press), the IOP sees another break request and starts the abort cycle over from the beginning. RESOLUTION: Modify "mux_data_int" (hp2100_mux.c) to place the proper value in the input data register when a send interrupt is requested. STATUS: Fixed in Release 29. 9. PROBLEM: The parity status reported in the MUX input trace is incorrect. VERSION: Release 28. OBSERVATION: The parity bit (bit 15) of the received data word reflects the computed parity of the data bits: 1 for odd parity and 0 for even parity. However, when tracing the multiplexer lower (data) card, the reported parity is incorrect. For example: >>MUXL csrw: Input data is channel 0 | odd parity | 0003 The data value (3) has even parity, but it is reported as odd. CAUSE: The trace reporting string is correctly set to report odd parity for bit 15 set and even parity for bit 15 clear. However, the trace format structure specifies the starting bit as bit 0 instead of bit 15. So the report actually reflects the state of bit 0. RESOLUTION: Modify "lower_input_format" (hp2100_mux.c) to reflect the correct offset of the parity bit. STATUS: Fixed in Release 29. 10. PROBLEM: 2000/Access programs may hang during long printer output. VERSION: Release 28. OBSERVATION: When printing or punching a large amount of output data, an Access BASIC program may hang. Output generation stops for no apparent reason. The only recourse is to press the BREAK key to stop the program. CAUSE: There is a race condition between the system processor (SP) and the I/O processor (IOP) during output to non-shareable devices controlled by the IOP. The race occurs more frequently when a large amount of output is generated quickly. The cause is this code in subroutine #IPAL in the SP main program source (TSB.asm) that is used to send buffered output data to IOP-connected devices: LDA ERTMP SEND IOR ALB REQUEST JSB SDVRP,I CODE LDB #IPAL RETRIEVE INB BUFFER LDA B,I LENGTH JSB SDVRP,I SEND TO IOP SFS CH2 WAIT FOR JMP *-1 ACKNOWLEDGEMENT CLF 0 LIA CH2 RETRIEVE RESPONSE If this "allocate buffer" ("ALB") request is refused by the IOP because all output buffers are in use, the resulting "no buffer available" response will cause the SP to issue a "release buffers" command to the IOP and then suspend the user's program until the IOP sends a "wake up user" command to indicate buffer availability. When the line printer completes its operation on the current output buffer, the IOP frees it and then sends the command to the SP to resume the user's output. The problem occurs when the line printer completes just as the allocate buffer request is made. That request sends two words: the ALB request code and the buffer length. The IOP denies the request but then immediately follows it with the "wake up user" command to indicate that a buffer is now available. If the command arrives between the time the SP sends the buffer length word and the time it picks up the response, the user program will hang. This occurs because the response causes the SP to set a flag indicating that the user has been suspended for buffer availability. If the "wake up user" command arrives before that flag is set, the command is ignored. So the SP is waiting for the IOP to issue the wake up, but the IOP has already issued it. This leaves the suspension in force until the user aborts the program by pressing the BREAK key. Nominally, only about nine instructions execute between the STC CH2 (within the SDVRP subroutine) that causes an IOP to accept the buffer length word and the SFS CH2 (above) that detects that the IOP's acknowledgement has arrived. However, the SP's interrupt system is on during the above SFS CH2 / JMP *-1 loop, and the processor interconnect has the highest I/O interrupt priority. So if, say, a time-base generator interrupt occurs during the SFS loop, several dozen instructions may be executed before control returns to the loop. If, during that time, the IOP command arrives, the resulting higher-priority interrupt is handled before the loop return, and the command is ignored because the "user is suspended" flag has not been set. RESOLUTION: Modify "card_service" (hp2100_ipl.c) to ensure that an IOP status response is picked up before an IOP command if both are seen during the same poll and to insert a long delay between these actions. Note that this is a workaround, and not a solution, as there is no general way to ensure that the response is read by the SP program before a pending IOP command is recognized. That's because the SP does not read the responses of some commands it sends, so simply holding off input card commands until the output card data register is read will not work. STATUS: Fixed in Release 29. 11. PROBLEM: RTE-II hangs in DVR31 if a 7900 disc is mounted while running. VERSION: Release 28. OBSERVATION: Mounting a peripheral disc, i.e., unit 1-3, while RTE-II is running causes a hang within DVR31 (the RTE disc driver) when a :MC command is issued. For example, with a running system, doing: scp> attach DPC1 scratch.disc *RU,FMGR :MC,-10 ...causes the system to become unresponsive. The interrupt system is off, and execution is looping within the STATW subroutine within DVR31. Examination shows that STA[1] = 040000 (i.e., First Status). The driver issues a Seek command to unit 0 and then requests unit 1 status again. Because STA[1] has not changed, execution loops forever. If STA[1] is manually set to 000000, the driver exits, and RTE resumes normal operation. CAUSE: The Status Register on the 13210A interface is implemented in an unusual way. It consists of a set of D-type flip-flops whose D inputs are grounded, and whose individual asynchronous presets are tied to the various controller and currently selected disc drive status lines. The register is clocked, and therefore cleared synchronously, when any command OTHER than Status Check is issued. A Status Check command (as well as a Write, Read, Check Data, or Initialize command) gates the status signals to the preset inputs. The register is therefore "ones-catching," and one-to-zero transitions will not be seen by repeated Status Check commands unless some other command intervenes to clear the register first. When the selected drive receives a Status Check command, it also asserts an internal CLEAR STATUS signal. This clears the Attention and First Status flip-flops on the drive after they are reported to the controller. When FMGR attempts to mount a newly attached disc image, DVR31 issues a Status Check command and sees the First Status bit set. The driver checks to see if the drive had been previously "downed" by a request for the unattached drive. If not, then it checks to see if a request is currently pending. If so, it issues (but does not complete) a Seek command, followed by another Status Check command. The incomplete Seek is necessary to clear the status register in order to see that First Status has transitioned from one to zero. The DP simulator neglected to clear the drive's First Status flip-flop after a Status Check command. Consequently, First Status was returned for subsequent Status Check commands, and DVR31 looped internally forever. RESOLUTION: Modify "dpd_svc" (hp2100_dp.c) to clear First Status as well as Attention when a Status Check command completes. STATUS: Fixed in Release 29. ====================== Release 28, 2018-05-23 ====================== This release of the HP 2100 simulator adds the following features: - The IPLI and IPLO devices now use shared memory instead of network sockets to simulate the 12875A Processor Interconnect kit that is used to communicate between the System Processor and the I/O Processor of the HP 2000B, C, F, and Access Time-Shared BASIC operating systems. This change, in addition to a new, adaptive service scheduling routine, improves data transfer time between the processes by a factor of 7 to 1. - Commands have been added to the IPL device to permit synchronization between the two simulator processes running the HP 2000 Time-Shared BASIC operating system. This greatly improves system startup reliability and permits the use of the HP-documented startup procedure of cross-loading the I/O Processor program from the System Processor. - The DIAGNOSTIC options of the IPLI and IPLO devices have been reworked to permit testing with the HP General Register Diagnostic as well as the Processor Interconnect Cable Diagnostic. - The DEBUG options of the IPLI and IPLO devices have been expanded. - The BOOT command now installs the correct binary loader for the CPU model. For example, BOOT PTR installs and runs the Basic Binary Loader (BBL) if the CPU is configured as a 2114/15/16 or 2100, or the 12992K Paper Tape Loader ROM if the CPU is configured as a 1000 M/E/F-Series. Prior releases installed the HP 1000 loader ROM regardless of the CPU model. - The LOAD command has been extended to permit copying of internal device boot loaders into memory. LOAD is identical to BOOT except that the CPU is neither preset nor run. In particular, LOAD CPU is the equivalent of pressing the IBL button on the HP 1000 front panel. - The new SET CPU ROMS command permits altering the set of preinstalled boot loader ROMs for 1000 CPUs. The new SHOW CPU ROMS command displays the currently installed set. - The -N (new file) option to the ATTACH command for disc devices now creates a full-size image file, equivalent to formatting the new disc before use. -------------------- Implementation Notes -------------------- - The abbreviated "SET CPU 21MX" command no longer sets the CPU to an E-Series model (i.e., to a 21MX-E, a.k.a. 1000-E); instead, it configures the CPU as an original 21MX (a.k.a. 1000-M). If an E-Series configuration is desired, it must be requested explicitly with the "SET CPU 21MX-E" command. - The "RESET -P CPU" command no longer restores the BBL to the protected memory area of 21xx machines. The "LOAD PTR" command may be used to perform this function. - The previous behavior of the "ATTACH -N" command for disc devices, i.e., creating a new zero-length image file, may be emulated by first deleting the file and then attaching it without specifying the -N switch. For instance, the "DELETE " and "ATTACH " commands produce a new zero-length file as "ATTACH -N " did before this change. The "ATTACH -N" behavior of other devices, e.g., magnetic tape drives and printers, did not change; a zero-length file is still created. - With the change to a shared-memory implementation, only a single "ATTACH IPL" command is required per instance to establish communication. The System Processor instance issues an "ATTACH -S IPL " command, and the I/O Processor instance must issue a corresponding "ATTACH -I IPL " command, where the parameter is a user-selected decimal number that identifies the instance pair. The prior "ATTACH [-L | -C] [ IPLI | IPLO ] " commands are deprecated but retained, so that existing command files will still work. However, they too will use shared memory rather than network connections. Consequently, the SP and IOP instances are now required to execute on the same machine, and the option is no longer supported. - Multiple consecutive CLC 0 instruction executions now cause only a single CRS assertion to the I/O devices. Therefore, IOBUS tracing when running HP 2000 Time-Shared BASIC systems no longer generates a pair of trace lines for each of the 131,072 consecutive CLC 0 executions typically used to initialize the 12920A Asynchronous Multiplexer. - The 12875A Processor Interconnect section of the HP2100 User's Guide has been revised to describe the new ATTACH protocol and process synchronization commands. - A list of device boot loaders installed for given device/CPU combinations has been added to the user's guide. - The "21MX-M" and "21MX-E" CPU options that had been inadvertently omitted from the last release of the user's guide have been restored. - The "Running HP 2000 Time-Shared BASIC on SIMH" monograph has been revised to cover the application of the new process synchronization commands to TSB startup command files. - Preconfigured software kits for 2000E, 2000F, and 2000 Access that employ the new shared memory and process synchronization commands are now available; see the "Available Software" section above for details. ---------- Bugs Fixed ---------- 1. PROBLEM: Serial port output stalls are not handled properly. VERSION: Release 27. OBSERVATION: The TTY, BACI, MPX, and MUX devices support I/O via host serial ports as well as via Telnet connections. While TTY, BACI, and MPX output via Telnet works correctly, output via serial ports fails. TTY output drops characters if the serial port stalls. Attempting to output to the BACI results in "Console Telnet output stall" and a simulator stop. Output to the MPX results in dropped characters and eventually an "IOPE" (parity error) message from RTE. CAUSE: The terminal multiplexer library (sim_tmxr.c, part of the SIMH framework) had provided a 256-byte output buffer for each line, independent of the connection type (Telnet or serial). The library was changed to reduce the serial buffer size to one byte. The BACI and MPX devices are internally buffered and default to a "FASTTIME" mode that sends the entire internal buffer to the library output routine. When the routine receives the second character, it returns SCPE_STALL status to indicate a buffer overflow. The device simulations did not expect and did not properly handle this status. The TTY and MUX devices are not buffered internally and were not affected by the loss of serial buffering. However, the TTY would drop output characters if the host serial buffer overflowed. RESOLUTION: Modify "tto_svc" (hp2100_stddev.c), "baci_term_svc" (hp2100_baci.c), and "line_service" (hp2100_mpx.c) to handle terminal multiplexer library buffer overflows properly. STATUS: Fixed in Release 28. 2. PROBLEM: The PTR device DIAGNOSTIC option shown in the user's guide does not exist. VERSION: Release 27. OBSERVATION: The "HP2100 Simulator User's Guide" says that specifying the DIAGNOSTIC option for the PTR device "converts the attached paper tape image into a continuous loop" for use by the paper tape reader diagnostic program. However, entering a "SET PTR DIAGNOSTIC" command gives a "Non-existent parameter" error. CAUSE: The option name specified in the PTR device's modifier table is "DIAG". It should be "DIAGNOSTIC" to match the option names used in the other device simulations. RESOLUTION: Modify "ptr_mod" (hp_stddev.c) to use the correct option name. STATUS: Fixed in Release 28. 3. PROBLEM: First Status is not cleared properly on the DP device. VERSION: Release 27. OBSERVATION: Execution of the RTE-I paper tape bootstrap for the 7900A and the 2000F loader for the 7900A halts with disc errors. The offending disc status word is 040001 octal, which denotes First Status and Any Error. Both programs expect disc status to be clear after an initial Seek and Read are performed. However, the disc drive and interface manuals state that First Status is cleared by a Status Check command, which is not being issued. CAUSE: Examination of the schematics in the 7900A Disc Drive Operating and Service Manual (07900-90002 February 1975) and the 13210A Disc Drive Interface Kit Operating and Service Manual (13210-90003 November 1974) shows that, contrary to the documentation, First Status is cleared on a Read, Write, Check Data, or Initialize command, as well as on a Status Check command. The current DP implementation follows the manual description rather than the schematics, so it fails to clear First Status when the initial Read is performed. RESOLUTION: Modify "dp_goc" (hp2100_dp.c) to clear First Status as well as Attention when one of the applicable commands is performed. STATUS: Fixed in Release 28. 4. PROBLEM: 2000F and Access will not boot from a 7900 drive using the BMDL. VERSION: Release 27. OBSERVATION: Attempting to boot Time-Shared BASIC from a 7900 using the Basic Moving-Head Disc Loader for the HP 2100 CPU results in a HLT 1 (unrecoverable disc error) in the TSB loader. Booting the same system with the 12992A loader ROM for the HP 1000 succeeds. The BMDL configures DMA for an oversize (~32000 word) transfer and expects the disc to terminate the operation with End of Cylinder (EOC) status. The TSB bootstrap successfully loads into memory. When it starts, it issues a CLC 0,C followed by a Check Status command that is expected to return zero, i.e., all status bits clear. However, the EOC bit is set, and the bootstrap halts with a HLT 1. CAUSE: The "Disc Interface 1 PCA Schematic Diagram" in the HP 13210A Disc Drive Interface Kit Operating and Service Manual (13210-90003, August 1974) shows that the CRS signal, which is generated by the CLC 0 instruction, does not affect the Status Register contents. However, examination of an actual hardware interface PCA shows that CRS assertion does clear the register. RESOLUTION: Modify "dpcio" (hp2100_dp.c) to clear the status register on receipt of a CRS signal. Note that later versions of the service manual (May 1975 and May 1978) show the correct CRS connection. STATUS: Fixed in Release 28. 5. PROBLEM: Forcibly disconnected 2000E multiplexer ports are unresponsive. VERSION: Release 27. OBSERVATION: The HP Time-Shared BASIC system sets a limit on the time allowed between dataset connection and login. By default, this is 120 seconds but may be changed by the PHONES system operator command. If the user does not complete a login within the time allowed, the dataset will be disconnected. This action occurs as expected on the 2000E system, but while reconnecting to the port succeeds, the line is unresponsive. More importantly, attempting to SLEEP the system hangs after responding to the "MAG TAPE SLEEP?" question. CAUSE: Examining the source code where the SLEEP hang occurs shows that the system is waiting in a loop for output to complete on the disconnected port. The forced disconnect code, which is shared by the PHONES, KILLID, and SLEEP commands, calls the BYE processor to log out an active user. However, for a PHONES disconnect, the user is not logged in. The BYE processor handles this condition correctly, but it returns to a common routine (LLEND) that outputs a line feed to the port. The multiplexer simulation omits a write to a disconnected port but also erroneously omits the output completion interrupt request. Consequently, TSB believes that the output is still in progress and therefore waits, in an infinite loop, for the completion interrupt that never occurs. Also, while the port is in output mode, input is turned off, so the port appears to be unresponsive when reconnected. RESOLUTION: Modify "muxo_svc" (hp2100_mux.c) to set "mux_xdon" to 1 to trigger the completion interrupt regardless of whether or not the port is connected to a Telnet session. STATUS: Fixed in Release 28. ====================== Release 27, 2017-09-06 ====================== This release of the HP 2100 simulator adds the following features: - Support for the HP 2613, 2617, and 2618 line printers has been added to the LPT device. The default printer remains the HP 2607. - The LPT device simulation has been rewritten to support realistic and optimized timing, compact and expanded output modes, custom VFU tape images, and tracing of internal operations. - The LOAD command has been rewritten to load files containing absolute binary loaders into the protected address space of the 21xx machines and configure the I/O instructions. For the 1000, LOAD can also be used to load boot loader ROM images other than those provided directly by the simulator. - The DUMP command has been added to write the binary loader currently resident in memory to an absolute binary file. - The TTY punch unit and the LPS, LPT, and PTP devices now position a newly attached file at the end of the file rather than at the start. As a result, output will append to, rather than overwrite, the existing content. - The DA, DP, DQ, and DS disc devices add the PROTECT and UNPROTECT options. These replace the now-deprecated LOCKED and WRITEENABLED options and more accurately reflect the labelling of the data protection switches on the disc drives. - The simulator message that is displayed when a programmed halt occurs has been changed to indicate that the halt code comes from the T-register value. - The Basic Binary Loader (BBL) is now installed by default in the 21xx machines. It is automatically configured to the select code of the paper tape reader. It may be overwritten with a different loader (e.g., the Basic Binary Disc Loader or Basic Moving-head Disc Loader) using the LOAD command. Performing a power-on reset of the CPU reinstalls the BBL. - Symbolic display and entry has been rewritten to improve efficiency and expanded to cover the full instruction set including optional microcode extensions that are currently enabled. - CPU instruction execution and data accesses may be selectively traced. The resulting trace listing is similar to the output of a logic analyzer connected to the CPU and I/O buses. - DMA/DCPC commands, status, and data accesses may be selectively traced. - TBG commands, status, and service entries may be selectively traced. - The DIAG option of the TBG device has been replaced with the REALTIME, W1A, W1B, W2A, and W2B options. Configuring the TBG to run its diagnostic now uses the REALTIME and W2B options, and restoring the normal configuration uses the CALTIME and W2A options. The W1A and W1B options extend the software compatibility of the TBG. - The MUXM device has been renamed MUXC to reflect that it is the multiplexer control card. The previous MUXM name is deprecated but will still work in existing simulation command files. - The multiplexer control card (MUXC) may be enabled and disabled independently of the upper and lower data cards (MUX and MUXL), reflecting its optional status in hardware configurations. - Memory address parsing for commands has been changed to add . format for physical addresses, where both the page and the offset range from 0 to 1777 octal. Linear addressing is now restricted to the 32K logical address space (0 to 77777 octal). Memory display uses linear addressing for locations within the logical address space; locations above 32K use the physical address format. - The previously separate STOP_INST, STOP_DEV, STOP_IOE, and INDMAX pseudo-registers used to stop the simulator under certain conditions have been replaced by the SET CPU STOP=[,...] and the SET CPU INDIR= commands. Stops may be temporarily bypassed by adding the -B switch to the command that resumes execution. - The HP 2100 Simulator User's Guide has been rewritten and significantly expanded. -------------------- Implementation Notes -------------------- - The simulator passes the HP 2613/17/18 line printer diagnostic as described in the "hp2100_diag.txt" file. - The line printer terminates each print line with the HP-standard CR/LF pair. If the output file is to be retained as a text file on a Unix system, removal of the carriage returns, e.g., via the "dos2unix" utility, may be desirable. - The LOAD command can no longer be used to read general absolute binary paper tape images into memory. The ATTACH PTR and BOOT PTR commands must now be used to read paper tapes. - The OS, OSTBG, VMA, EMA, VIS, and SIGNAL CPU debug flags have been removed. Tracing of these firmware instructions is now performed by specifying SET CPU DEBUG=EXEC and SET CPU EXEC with the appropriate opcode range and mask, as follows: * SET CPU DEBUG=OS => SET CPU EXEC=105340;177760 * SET CPU DEBUG=VMA => SET CPU EXEC=105240;177760 * SET CPU DEBUG=EMA => SET CPU EXEC=105240;177760 * SET CPU DEBUG=VIS => SET CPU EXEC=101460;173760 * SET CPU DEBUG=SIGNAL => SET CPU EXEC=105600;177760 - The separate tracing of time-base generator interrupt instructions provided by the OS and OSTBG CPU debug flags is no longer supported. Entering the replacement command above traces all OS instructions, including the TBG interrupt instructions. - The TIMER, RRR 16, .FLUN, and the OS/VMA, VIS, and SIGNAL self-test instructions are no longer exempt from the undefined/unimplemented instruction stop tests. Attempted execution of these instructions without the appropriate firmware options installed will cause simulation stops if the UNDEF (TIMER and RRR) or UNIMPL (.FLUN and self-tests) option is enabled. Because of this change, the default state of the unimplemented instruction stop has been reversed from "on" to "off". - The "stop on I/O error" features controlled by the STOP_IOE register values have been removed from the DR, LPS, LPT, MSC, MTC, and PTP devices, as all of these report I/O error status to the CPU via their interface input registers. STOP_IOE has been removed from the PTR device and replaced with SET CPU STOP=IOERR, as this device does not report I/O error status to the CPU through its interface. - The LOCKED and WRITEENABLED options for the MSC and MTC devices are deprecated. The supported method of write-protecting a tape drive is to attach the tape image with the -R (read-only) switch or by setting the host operating system's read-only attribute on the tape image file. This simulates removing the write ring from the tape reel before mounting it on the drive. There is no hardware method of write-protecting a mounted and positioned tape reel. - If the previous ATTACH behavior (overwriting rather than appending) is desired for the TTY punch unit and the LPS, LPT, and PTP devices, set the device's (P)POS register to 0 after attaching. ---------- Bugs Fixed ---------- 1. PROBLEM: EXAMINE -M for addresses > 32K displays misleading operands. VERSION: Release 26. OBSERVATION: Current-page memory references of instructions residing above the 32K logical address space are printed as though they reside at their locations modulo 32K. For example, DEPOSIT 170001 026020 and EXAMINE -M 170001 displays JMP 70020, and DEPOSIT 200001 026020 displays JMP 20. CAUSE: The printed addresses assume that the instructions will be executed from their respective pages (modulo 32). However, instructions can be executed only when they are mapped into the logical address space, and any given physical page may be mapped to any arbitrary logical page. Therefore, the address printed may not represent the actual logical address after mapping. RESOLUTION: Modify "fprint_cpu" (hp2100_sys.c) to use Z/C address notation for memory references in instructions residing in physical memory above 32K. STATUS: Fixed in Release 27. 2. PROBLEM: Enabling IOP firmware should not be allowed on the 1000 F-Series. VERSION: Release 26. OBSERVATION: The command "SET CPU 1000-F,IOP" is allowed, but it should not be, as the IOP firmware is not supported on this machine. CAUSE: The F-Series does not provide the firmware mapping table entries that permit operation of the 2000/Access I/O Processor firmware. IOP instruction opcodes 10x400-17 and 10x420-37 are marked as "HP Reserved" in the F-Series mapping table, and opcodes 10x460-77 are dedicated to the VIS microcode. RESOLUTION: Modify the "cpu_features" array (hp2100_cpu.c) to remove the IOP option from the 1000 F-Series entry. STATUS: Fixed in Release 27. 3. PROBLEM: A rejected model change still changes the CPU options. VERSION: Release 26. OBSERVATION: Changing to a CPU model that does not support the current memory size will reduce memory to the maximum supported by the new model. If the truncated portion contains non-zero values, the simulator will ask for confirmation before proceeding. If the truncation is rejected, the CPU options are still set to those of the new model, even though the old model is retained. For example: sim> SET CPU 1000-F,128K sim> SHOW CPU CPU idle disabled 128KW, 1000-F, EAU FP, no IOP, DMS FFP, DBI, no EMA/VMA no VIS, no SIGNAL sim> DEPOSIT 100000 1 sim> SET CPU 2116 Really truncate memory [N]?NO Command not completed sim> SHOW CPU CPU idle disabled 128KW, 1000-F, no EAU no FP, no IOP, no DMS no FFP, no DBI, no EMA/VMA no VIS, no SIGNAL CAUSE: The CPU options are set before the memory size is changed, so when the size change is rejected, the new CPU options are retained. RESOLUTION: Modify "cpu_set_model" (hp2100_cpu.c) to perform the memory size change first, so that if it is rejected, the CPU options have not been changed. STATUS: Fixed in Release 27. 4. PROBLEM: Virtual memory mapping fails for accesses above 126 MB. VERSION: Release 26. OBSERVATION: A program using virtual memory provided by the RTE-6/VM operating system may access up to 128 MB of data, although VMA programs default to a 16 MB limit. Accesses to data in virtual memory are mapped through the last two DMS user map registers. Normally, each VMA access maps in the memory page corresponding to the virtual address plus the following memory page. This allows access to single items up to 1024 words in size starting at any offset within the (first) page. If a data item resides in the last 2 MB of virtual memory, access to an item that crosses the page boundary is incorrect. Instead of accessing words in the second page, the accesses wrap around within the first page. CAUSE: The suit number part of the virtual address is not restored before checking the allocation status of the page table entry corresponding to the second (spillover) page. As a result, an unallocated second page in the last 2 MB of virtual memory is seen as beyond the VM area limit, and instead of generating a page fault to allocate the second page, the map registers are set up to prevent access to the second page by setting the first page address into both map registers. RESOLUTION: Modify "cpu_vma_lbp" (hp2100_cpu5.c) to check for spill page allocation correctly. STATUS: Fixed in Release 27. 5. PROBLEM: Memory expansion is not disabled when DMS is disabled. VERSION: Release 26. OBSERVATION: If the Memory Expansion Module in a 1000-Series CPU has been enabled, and then the DMS firmware option is disabled or the CPU is changed to a model that does not support memory expansion (e.g., a 2100), memory expansion remains enabled. In this case, memory accesses should revert to physical addressing, but instead logical-to-physical address translation through the currently enabled map remains in effect. CAUSE: Disabling DMS should set the "dms_enb" flag to 0, but it does not. RESOLUTION: Modify "set_model" and "set_option" (hp2100_cpu.c) to clear the "dms_enb" flag if DMS is not enabled after the model or option change. STATUS: Fixed in Release 27. ====================== Release 26, 2017-05-01 ====================== This release of the HP 2100 simulator does not add any new features. -------------------- Implementation Notes -------------------- - Starting with the next release, the LOAD command will be rewritten to load files containing absolute binary loaders into the protected address space of the 21xx machines and configure the I/O instructions. The LOAD command is not designed for general loading of absolute binary files, as it does not initialize the A and B registers as some HP software expects. It is intended only to install bootstrap loaders. The BOOT PTR command is the proper simulation of the hardware absolute paper tape loader. ---------- Bugs Fixed ---------- 1. PROBLEM: The RWCS debug option shown in the user's guide does not exist. VERSION: Release 25. OBSERVATION: The "HP2100 Simulator User's Guide" says that the RWCS debug option may be specified for the DS and DA devices to trace "disk read/ write/control/status commands." However, entering a SET DS DEBUG=RWCS command gives an "Invalid argument" error. CAUSE: The option name is misspelled; the correct option is RWSC. RESOLUTION: Modify "hp2100_doc.doc" to list the correct option name. STATUS: Fixed in Release 26. 2. PROBLEM: Halt opcodes 1060xx and 1070xx do not display in mnemonic form. VERSION: Release 25. OBSERVATION: Halt instructions 106000-106077 and 107000-107077 are not displayed in mnemonic form, either directly with an EXAMINE -M command or in the message displayed for a programmed halt. These instruction ranges are displayed in octal only. CAUSE: Section 3.20, "Input/Output Instructions," of the "HP 1000 M/E/F-Series Computers Technical Reference Handbook" (HP 5955-0282, March 1980) says, in part, "Bit 11, where relevant, specifies the A- or B-register or distinguishes between set control and clear control; otherwise, bit 11 may be a logic 0 or a logic 1 without affecting the instruction (although the assembler will assign zeros in this case)." The HLT instruction does not specify the A/B register, so the valid opcodes are 102000-102077, 103000-103777, 106000-106077, and 107000-107077. However, the latter two ranges are omitted from the "opcode" and "opc_val" tables used for decoding. RESOLUTION: Add the 1060xx/107xx range to the "opc_val" table and a second "HLT" string to the "opcode" table (hp2100_sys.c) to permit mnemonic display of this instruction range. STATUS: Fixed in Release 26. 3. PROBLEM: The SFB (scan for byte) opcode displays as SBT (store byte). VERSION: Release 25. OBSERVATION: Entering the "EVAL -M 105767" command should display the "SFB" mnemonic. Instead, it displays "SBT". CAUSE: The entry in the opcode mnemonic table corresponding to the 105767 value is "SBT", which is incorrect. It should be "SFB" (SBT is 105764). RESOLUTION: Modify the "opcode" table (hp2100_sys.c) to use the correct mnemonic for the SFB instruction. STATUS: Fixed in Release 26. 4. PROBLEM: Host file system seek errors are not caught. VERSION: Release 25. OBSERVATION: The MAC/ICD disc library checks for host file system read or write errors and returns Uncorrectable Data Error status if an error is indicated. However, host file system seeks are simply assumed to succeed; no indication of an error is given if a call fails. A failed seek should be detected, and a Drive Fault (positioner error) should be returned. CAUSE: Oversight. RESOLUTION: Modify "position_sector" (hp2100_disclib.c) to test the "sim_fseek" call for error status and to simulate a Drive Fault (AGC error) if the call fails. STATUS: Fixed in Release 26. 5. PROBLEM: Set Flow Control and Cancel commands fail if port key is not set. VERSION: Release 25. OBSERVATION: HP 8-channel multiplexer commands that refer to ports do so indirectly by passing a port key, rather than a port number. The key-to-port translation is established by the "Set Port Key" command, which must be executed before any port-specific commands. If a port key has not been established, then all port-specific commands should be ignored. However, the "Cancel first receive buffer" and "Set flow control" commands cause program corruption if the key has not been set. CAUSE: The test for key validity is improperly applied for these commands. RESOLUTION: Modify "exec_command" (hp2100_mpx.c) to ignore these commands if the port key has not been set. STATUS: Fixed in Release 26. 6. ENHANCEMENT: Improve the EAU shift and rotate instruction simulations. VERSION: Release 25. OBSERVATION: The shift and rotate instructions (ASL, ASR, LSL, LSR, RRL, and RRR) perform 32-bit operations on the combined B and A registers. The original implementation treated the 16-bit registers independently. However, it is faster and smaller to form a 32-bit operand, apply the operation, and then split the operand back into the B and A registers. Modern compilers, such as gcc, recognize the shifting and masking patterns necessary for a rotation and generate a single rotate-left or rotate-right machine instruction. RESOLUTION: Modify "cpu_eau" (hp2100_cpu1.c) to reimplement the shift and rotate instructions as 32-bit operations. STATUS: Fixed in Release 26. ====================== Release 25, 2017-01-11 ====================== This is the initial checkpoint release of the HP 2100 simulator, corresponding to the 25th set of changes to the simulator code base. The following devices are currently simulated: - 2114C CPU with up to 16 KW of memory - 2115A CPU with up to 8 KW of memory - 2116C CPU with up to 32 KW of memory - 2100A CPU with up to 32 KW of memory - 1000 M/E/F-Series CPU with up to 1024 KW of memory - EAU, FP, IOP, DMS, FFP, DBI, VIS, and SIGNAL microcode extensions - RTE-IV EMA or RTE-6/VM OS and VMA microcode extensions - 12531C Buffered Teleprinter Interface with one 2752 Teleprinter - 12539C Time Base Generator - 12557A Disc Controller with four 2870 drives - 12559C Magnetic Tape Controller with one 3030 drive - 12565A Disc Controller with two 2883 drives - 12566B Microcircuit Interface with a loopback connector - 12578A Direct Memory Access Controller - 12581A Memory Protect - 12597A Duplex Register Interface with one 2748 Paper Tape Reader - 12597A Duplex Register Interface with one 2895 Paper Tape Punch - 12606B Fixed Head Disc Controller with one 2770/2771 drive - 12607B Direct Memory Access Controller - 12610B Drum Controller with one 2773/2774/2775 drive - 12620A Privileged Interrupt Fence - 12653A Printer Controller with one 2767 Line Printer - 12792C 8-Channel Asynchronous Multiplexer - 12821A Disc Interface with four 7906H/7920H/7925H drives - 12845B Printer Controller with one 2607 Line Printer - 12875A Interprocessor Link - 12892B Memory Protect - 12895A Direct Memory Access Controller - 12897B Dual-Channel Port Controller - 12920A 16-Channel Terminal Multiplexer - 12936A Privileged Interrupt Fence - 12966A Buffered Asynchronous Communications Interface - 13037D Disc Controller with eight 7905/7906/7920/7925 drives - 13181A Magnetic Tape Controller with four 7970B drives - 13183A Magnetic Tape Controller with four 7970E drives - 13210A Disc Controller with four 7900 drives The "HP 2100 Simulator User's Guide" manual describes the configuration and operation of each of these devices in detail. -------------------- Implementation Notes -------------------- - New bug fixes will now be listed in this file under the associated release rather than in their previous location (hp2100_bugfixes.txt). - Starting with the next release, the LOAD command will restrict its operation to the addresses occupied by the bootstrap loaders, i.e., the last 64 locations in memory (up to 32K). The LOAD command is not designed for general loading of absolute binary files, as it does not initialize the A and B registers as some HP software expects. It is intended only to install bootstrap loaders. The BOOT PTR command is the proper simulation of the hardware absolute paper tape loader. ---------- Bugs Fixed ---------- 1. PROBLEM: DPC device documentation uses the wrong disc drive model number. VERSION: Release 24. OBSERVATION: The comments in the hp2100_dpc.c source file and Section 2 of the "HP2100 Simulator User's Guide" say that the DPC device supports the 2871 disc drive, while Section 2.6.1 of the User's Guide says that the support is for the 2781 disc drive. Neither of these model numbers is correct. Contemporaneous literature (e.g., the "2116B Computer Price List," dated June 1970) states that the disc memory subsystem consists of the HP 2870A Moving Head Disc, HP 2871A Disc Controller, HP 2881A Power Supply, and HP 2882A Cabinet. CAUSE: The controller model number is used instead of the drive model number, while the "2781" number is a transposition of "2871." RESOLUTION: Modify the initial comments in the DPC device source file (hp2100_dpc.c) and modify the sections of the HP2100 Simulator User's Guide to use the correct disc drive model number (2870). STATUS: Fixed in Release 25. 2. PROBLEM: The BOOT DRC command does not execute correctly. VERSION: Release 24. OBSERVATION: Attempting to boot DOS from a fixed-head disc or drum does not work. The CPU sits in a loop waiting for DMA to finish, but it never does. CAUSE: The DMA control word in the DR device bootstrap is not configured during BOOT DRC processing, so DMA is communicating with the wrong device. RESOLUTION: Modify "drc_boot" (hp2100_dr.c) to set the fixed disc/drum select code into the DMA control word before returning. STATUS: Fixed in Release 25. 3. PROBLEM: The valid command "DEPOSIT 2000 JMP 2001" is rejected. VERSION: Release 24. OBSERVATION: Regarding symbolic input, the HP2100 User's Manual says that the "C" and "Z" flags, signifying a current-page or zero-page reference, respectively, are not needed "...when entering [memory reference] instructions into CPU memory; the simulator figures out from the target address what mode to use." While the valid command "DEPOSIT 1000 JMP 1001" correctly enters a zero-page jump into memory, the valid command "DEPOSIT 2000 JMP 2001" does not enter a current-page jump. Instead, an "Invalid argument" error occurs. CAUSE: The "parse_sym" routine looks for the optional "C" or "Z" flag when parsing memory reference instructions and sets a flag if either is specified. The test for a current-page reference is performed only if the reference type was not explicitly specified. However, the sense of the test is reversed. RESOLUTION: Modify "parse_sym" (hp2100_sys.c) to correct the test for C/Z option specification. STATUS: Fixed in Release 25. 4. PROBLEM: The invalid command "DEPOSIT 2000 JMP C 2001" is accepted. VERSION: Release 24. OBSERVATION: Regarding symbolic input, the HP2100 User's Manual says that "The address is an octal number in the range 0 - 77777; if C or Z is specified, the address is a page offset in the range 0 - 1777." However, specifying a page offset > 1777 is accepted without complaint if it is within the current page range. CAUSE: Error checking for memory reference instruction entry is incomplete. RESOLUTION: Modify "parse_sym" (hp2100_sys.c) to ensure that the range check is enforced if either C or Z is specified. STATUS: Fixed in Release 25. 5. PROBLEM: Punched output does not appear on TTY devices lacking a paper tape punch. VERSION: Release 24. OBSERVATION: Running the HP contributed library program "HP 2000F BASIC for DOS-M/DOS III" does not produce any console output when using terminal driver DVR00 as required by the program. When using alternate terminal driver DVR05, console output appears but console input does not work properly. CAUSE: DOS-M and DOS-III support two modes of console I/O: ASCII mode and binary mode. ASCII mode appends carriage-return/line-feed characters on output and strips them on input. Binary mode sends and receives bytes exactly as supplied. DVR00 is required because DVR05 does not support the binary I/O mode required by the program. However, DVR00 assumes that a binary write is to be directed to the console's paper tape punch rather than the console printer and therefore sets the TTY interface's "punch flip-flop" instead of the "print flip-flop" to accompany the text output. The simulation of the HP 12531 interface card associated with the TTY device discards output if the punch flip-flop is set and the punch unit (TTY2) is not attached. The problem occurs because only a connected HP 2754 teleprinter (a modified Teletype ASR35) reacts to the print and punch flip-flop signals. All other supported terminal devices ignore the signals and print whatever output is supplied (an HP 2752 -- a rebadged ASR33 -- has a manual control for the punch, but the punch and printer operate together when the punch is on). The 2000F BASIC program apparently was designed for use with one of these other terminals, which print normally even though only the punch flip-flop is set. RESOLUTION: Modify "tto_out" (hp2100_stddev.c) to honor the print and punch flip-flop settings and separate the output as directed only if the console punch unit is attached (simulating an HP 2754). When the unit is detached, all output is delivered to the console printer, regardless of the flip-flop settings (simulating all other console devices). STATUS: Fixed in Release 25.