HP2100: Release 30

HP2100/hp2100_cpu.c

@@ -1,7 +1,7 @@
 /* hp2100_cpu.c: HP 21xx/1000 Central Processing Unit simulator
 
    Copyright (c) 1993-2016, Robert M. Supnik
-   Copyright (c) 2017-2019, J. David Bryan
+   Copyright (c) 2017-2020, J. David Bryan
 
    Permission is hereby granted, free of charge, to any person obtaining a copy
    of this software and associated documentation files (the "Software"), to deal
@@ -28,6 +28,10 @@
                 I/O subsystem
                 Power Fail Recovery System
 
+   26-Aug-20    JDB     Fixed tracing for I/O error simulation stops
+                        Corrected line ends for trace to stdout
+                        "set_model" now clears the X and Y registers for 21xx CPUs
+   04-Jul-20    JDB     Postlude trace now calls "sim_error_text" unconditionally
    08-Dec-19    JDB     Added "hp_reset_poll" call to "cpu_reset"
    03-Jul-19    JDB     Substituted BP_EXEC for explicit 'E' switch in sim_brk_test
    08-Apr-19    JDB     Suppress stop messages for step and breakpoints in DO files
@@ -2140,6 +2144,9 @@ while (status == SCPE_OK) {                             /* execute until simulat
             fprint_val (sim_deb, sim_eval [0], cpu_dev.dradix,          /*   then print the numeric */
                         cpu_dev.dwidth, PV_RZRO);                       /*     value again */
 
+        if (sim_deb == stdout)                          /* if debug output is to the (raw) console */
+            fputc ('\r', sim_deb);                      /*   then insert a carriage return */
+
         fputc ('\n', sim_deb);                          /* end the trace with a newline */
         }
 
@@ -2190,12 +2197,20 @@ pcq_r->qptr = pcq_p;                                    /* update the PC queue p
 sim_brk_dflt = meu_breakpoint_type (FALSE);             /* base the default breakpoint type on the current MEM state */
 
 if (TRACING (cpu_dev, cpu_dev.dctrl)                    /* if instruction tracing is enabled */
-  && status <= SCPE_LAST)                               /*   and the status is valid */
+  && status <= SCPE_LAST) {                             /*   and the status is valid */
     hp_trace (&cpu_dev, cpu_dev.dctrl,                  /*     then output the simulation stop reason */
-              DMS_FORMAT "simulation stop: %s\n",
+              DMS_FORMAT "simulation stop: %s",
               meu_indicator, meu_page, MR, TR,
-              status >= SCPE_BASE ? sim_error_text (status)
+              sim_error_text (status));
-                                  : sim_stop_messages [status]);
+
+    if (cpu_ioerr_uptr)                                 /* if this is an I/O error stop */
+        sim_vm_fprint_stopped (sim_deb, status);        /*   then add additional information */
+
+    if (sim_deb == stdout)                              /* if debug output is to the (raw) console */
+        fputc ('\r', sim_deb);                          /*   then insert a carriage return */
+
+    fputc ('\n', sim_deb);                              /* tie off the line */
+    }
 
 if (sim_switches & SIM_SW_HIDE                          /* if executing in a non-echoing command file */
   && (status == SCPE_STEP || status == STOP_BRKPNT))    /*   and a step or breakpoint stop occurs */
@@ -3795,6 +3810,10 @@ return SCPE_OK;
        For logical tests that depend on this, it is faster (by one x86 machine
        instruction) to test the "cpu_configuration" variable for the presence of
        one of the three 1000 model flags.
+
+    3. The index registers (X and Y) are cleared when the model is set to a 21xx
+       CPU, which does not have index registers.  This is required for the
+       "mem_trace_registers" routine to omit the registers from the trace.
 */
 
 static t_stat set_model (UNIT *uptr, int32 new_model, char *cptr, void *desc)
@@ -3836,6 +3855,8 @@ if (result == SCPE_OK) {                                /* if the change succeed
     else {                                              /* otherwise this is a 2100 or 211x */
         is_1000 = FALSE;                                /*   so set the model index */
         mem_end = mem_size - IBL_SIZE;                  /*     and reserve memory for the loader */
+
+        XR = YR = 0;                                    /* clear the (non-existent) index registers */
         }
     }
 

HP2100/hp2100_defs.h

@@ -1,7 +1,7 @@
 /* hp2100_defs.h: HP 2100 simulator architectural declarations
 
    Copyright (c) 1993-2016, Robert M. Supnik
-   Copyright (c) 2017-2019, J. David Bryan
+   Copyright (c) 2017-2020, J. David Bryan
 
    Permission is hereby granted, free of charge, to any person obtaining a copy
    of this software and associated documentation files (the "Software"), to deal
@@ -24,6 +24,7 @@
    used in advertising or otherwise to promote the sale, use or other dealings
    in this Software without prior written authorization from the authors.
 
+   17-Aug-20    JDB     Corrected "cputc" definition
    08-Dec-19    JDB     Added "hp_reset_poll" routine declaration
    28-Mar-19    JDB     Added extensions
    18-Mar-19    JDB     Added include for SCP extensions
@@ -308,7 +309,7 @@
 
 #define cputc(ch) \
           do { \
-              putc (ch); \
+              putchar (ch); \
               if (sim_log) \
                   fputc (ch, sim_log); \
               } \

HP2100/hp2100_lpt.c

@@ -1,7 +1,7 @@
 /* hp2100_lpt.c: HP 2100 12845B Line Printer Interface simulator
 
    Copyright (c) 1993-2016, Robert M. Supnik
-   Copyright (c) 2017-2019, J. David Bryan
+   Copyright (c) 2017-2020, J. David Bryan
 
    Permission is hereby granted, free of charge, to any person obtaining a copy
    of this software and associated documentation files (the "Software"), to deal
@@ -26,6 +26,7 @@
 
    LPT          HP 12845B Line Printer Interface
 
+   16-Mar-20    JDB     Corrected introductory comments.
    09-Dec-19    JDB     Removed redundant SIM_SW_REST check in "lp_attach"
    01-Oct-19    JDB     DETACH -F now flushes the print buffer if not empty
    26-Jun-18    JDB     Revised I/O model
@@ -221,6 +222,7 @@
    The format commands recognized by the printers are:
 
      0 0 0 0 0 0 0 -- slew 0 lines (suppress spacing) after printing *
+     0 0 0 0 0 0 1 -- slew 1 line after printing
           ...
      0 0 0 1 1 1 1 -- slew 15 lines after printing
 
@@ -228,7 +230,7 @@
           ...
      0 1 1 1 1 1 1 -- slew 63 lines after printing **
 
-      * slew 1 line on the 2607A, which cannot suppress printing.
+      * slew 1 line on the 2607A, which cannot suppress spacing after printing
      ** available only on the 2610A and 2614A
 
    and:

HP2100/hp2100_mem.c

@@ -1,7 +1,7 @@
 /* hp2100_mem.c: HP 21xx/1000 Main Memory/Memory Expansion Module/Memory Protect simulator
 
    Copyright (c) 1993-2016, Robert M. Supnik
-   Copyright (c) 2017-2019, J. David Bryan
+   Copyright (c) 2017-2020, J. David Bryan
 
    Permission is hereby granted, free of charge, to any person obtaining a copy
    of this software and associated documentation files (the "Software"), to deal
@@ -29,6 +29,7 @@
    MEM          12731A Memory Expansion Module
    MP           12581A/12892B Memory Protect
 
+   26-Aug-20    JDB     Consolidated "mem_trace_registers" E/O/I output
    27-Mar-19    JDB     "dm_violation" now correctly freezes the violation register
    02-Aug-18    JDB     Added MEM device
    30-Jul-18    JDB     Renamed "iop_sp" to "SPR" (stack pointer register)
@@ -321,25 +322,29 @@ static const uint32 tbg  = 0001674u;            /* (RTE) TBG address */
 
 /* Main memory tracing constants */
 
-static const char * const register_values [] = {    /* register values, indexed by EOI concatenation */
-    "e o i",                                        /*   E = 0, O = 0, interrupt_system = off */
-    "e o I",                                        /*   E = 0, O = 0, interrupt_system = on */
-    "e O i",                                        /*   E = 0, O = 1, interrupt_system = off */
-    "e O I",                                        /*   E = 0, O = 1, interrupt_system = on */
-    "E o i",                                        /*   E = 1, O = 0, interrupt_system = off */
-    "E o I",                                        /*   E = 1, O = 0, interrupt_system = on */
-    "E O i",                                        /*   E = 1, O = 1, interrupt_system = off */
-    "E O I"                                         /*   E = 1, O = 1, interrupt_system = on */
-    };
-
 static const char mp_value [] = {               /* memory protection value, indexed by mp_control */
     '-',                                        /*   MP is off */
     'P'                                         /*   MP is on */
     };
 
-static const char * const register_formats [] = {       /* CPU register formats, indexed by is_1000 */
+static const char e_value [] = {                /* extend register value */
-    REGA_FORMAT "  A %06o, B %06o, ",                   /*   is_1000 = FALSE format */
+    'e',                                        /*   E is 0 */
-    REGA_FORMAT "  A %06o, B %06o, X %06o, Y %06o, "    /*   is_1000 = TRUE  format */
+    'E'                                         /*   E is 1 */
+    };
+
+static const char o_value [] = {                /* overflow register value */
+    'o',                                        /*   O is 0 */
+    'O'                                         /*   O is 1 */
+    };
+
+static const char i_value [] = {                /* interrupt system value */
+    'i',                                        /*   interrupt system is off */
+    'I'                                         /*   interrupt system is on */
+    };
+
+static const char * const register_formats [] = {               /* CPU register formats, indexed by is_1000 */
+    REGA_FORMAT "  A %06o, B %06o, %.0u%.0u%c %c %c\n",         /*   is_1000 = FALSE format */
+    REGA_FORMAT "  A %06o, B %06o, X %06o, Y %06o, %c %c %c\n"  /*   is_1000 = TRUE  format */
     };
 
 static const char * const mp_mem_formats [] = {                 /* MP/MEM register formats, indexed by is_1000 */
@@ -1252,6 +1257,9 @@ else                                                    /* otherwise */
     1. The "is_1000" flag is used to include or omit, based on the CPU model,
        the X and Y registers from the working register trace and the MEVR and
        MESR from the memory protection trace.
+
+    2. The "%.0u" print specifications in the trace call absorb the zero X and Y
+       register values without printing them when the CPU is not a 1000.
 */
 
 void mem_trace_registers (FLIP_FLOP interrupt_system)
@@ -1260,10 +1268,9 @@ hp_trace (&cpu_dev, TRACE_REG,              /* output the working registers */
           register_formats [is_1000],       /*   using a format appropriate for the CPU model */
           mp_value [mp_control],
           meu_status & MEST_FENCE_MASK,
-          SR, AR, BR, XR, YR);
+          SR, AR, BR, XR, YR,
-
+          e_value [E], o_value [O],
-fputs (register_values [E << 2 | O << 1 | interrupt_system], sim_deb);  /* output E, O, and interrupt system */
+          i_value [interrupt_system]);
-fputc ('\n', sim_deb);
 
 if (mp_mem_changed) {                       /* if the MP/MEM registers have been altered */
     hp_trace (&cpu_dev, TRACE_REG,          /*   then output the register values */

HP2100/hp2100_mux.c

@@ -26,6 +26,7 @@
 
    MUX,MUXL,MUXC        12920A Asynchronous Multiplexer Interface
 
+   21-Oct-20    JDB     ATTACH/DETACH MUXL <port> command is now rejected
    03-Jan-20    JDB     Revised modem control operation, added "muxc_reset"
    23-Oct-19    JDB     Fixed "muxl_ibuf" value for send interrupts
                         Fixed "lower_input_format" starting bit number
@@ -1985,7 +1986,7 @@ static t_stat muxl_attach (UNIT *uptr, char *cptr)
 {
 t_stat status;
 
-status = tmxr_attach_unit (&mux_desc, &mux_poll, uptr, cptr);   /* try to attach to the serial port */
+status = tmxr_attach_unit (&mux_desc, NULL, uptr, cptr);   /* try to attach to the serial port */
 
 if (status == SCPE_OK) {                                /* if the attach succeeded */
     muxu_unit [0].wait = POLL_FIRST;                    /*   then set up the poll */
@@ -2003,7 +2004,7 @@ static t_stat muxl_detach (UNIT *uptr)
 t_stat status;
 int32  line;
 
-status = tmxr_detach_unit (&mux_desc, &mux_poll, uptr); /* try to detach the serial port */
+status = tmxr_detach_unit (&mux_desc, NULL, uptr); /* try to detach the serial port */
 
 if (status == SCPE_OK) {                                /* if the detach succeeded */
     line = uptr - muxl_unit;                            /*   then determine the line number */

HP2100/hp2100_sys.c

@@ -1,7 +1,7 @@
 /* hp2100_sys.c: HP 2100 system common interface
 
    Copyright (c) 1993-2016, Robert M. Supnik
-   Copyright (c) 2017-2019, J. David Bryan
+   Copyright (c) 2017-2020, J. David Bryan
 
    Permission is hereby granted, free of charge, to any person obtaining a copy
    of this software and associated documentation files (the "Software"), to deal
@@ -24,6 +24,8 @@
    used in advertising or otherwise to promote the sale, use or other dealings
    in this Software without prior written authorization from the authors.
 
+   26-Aug-20    JDB     Modified "hp_trace" to output CR LFs to stdout
+   25-Aug-20    JDB     Now sets SCP hooks in "one_time_init" routine
    08-Dec-19    JDB     Added "hp_reset_poll" and "poll_name" routines
    04-Mar-19    JDB     Added "sim_vm_release" character string declaration
    04-Oct-18    JDB     Reordered the device list alphabetically
@@ -117,9 +119,9 @@
 
 
 
-/* Global release string */
+/* Release string */
 
-char *sim_vm_release = "29";                    /* HP 2100 simulator release number */
+static char *hp_release = "30";                 /* HP 2100 simulator release number */
 
 
 /* Command-line switch parsing from scp.c */
@@ -3395,6 +3397,11 @@ return;
    name among the devices enabled for tracing to ensure that all trace lines
    will align for easier reading.
 
+   Because the prefix is output only once, embedded newlines should not be
+   present in the format string.  If multiple output lines are desired, then
+   this routine should be called multiple times, so that each line receives an
+   identifying trace prefix.
+
 
    Implementation notes:
 
@@ -3403,6 +3410,23 @@ return;
        the latter, we must allocate "sufficiently large" arrays for the flag
        name and format, rather than arrays of the exact size required by the
        call parameters.
+
+    2. If the trace output is being written to stdout, a terminating LF must
+       be translated to CR LF.  This is because the console is in "raw" mode
+       while the CPU is executing instructions.  Output to a file does not need
+       this processing, as text mode handles the host line-end convention.
+
+    3. Handling embedded newlines properly would require multiple calls to
+       "vfprintf", each preceded by the prefix, and each having a format string
+       consisting of the next segment that ends with an embedded newline.
+       However, multiple calls are not allowed.  The C standard says:
+
+         "As the functions vfprintf [etc.] invoke the va_arg macro, the value of
+          arg after the return is indeterminate."
+
+       So there is no way to have the second (e.g.) call start with those
+       (variable) parameters not consumed by the prior call.  Consequently, the
+       terminating LF check need only be done at the end of the format string.
 */
 
 #define FLAG_SIZE           32                          /* sufficiently large to accommodate all flag names */
@@ -3434,15 +3458,25 @@ if (sim_deb != NULL && dptr != NULL) {                  /* if the output stream
                          (int) device_size, sim_dname (dptr),   /*   while padding the device and flag names */
                          (int) flag_size, flag_name);           /*     as needed for proper alignment */
 
-                va_start (argptr, flag);                        /* set up the argument list */
+                va_start (argptr, flag);                /* set up the argument list */
 
-                format = va_arg (argptr, char *);               /* get the format string parameter */
+                format = va_arg (argptr, char *);       /* get the format string parameter */
-                strcat (header_fmt, format);                    /* append the supplied format */
+                strcat (header_fmt, format);            /* append the supplied format */
 
-                vfprintf (sim_deb, header_fmt, argptr);         /* format and print to the debug stream */
+                if (sim_deb == stdout) {                            /* if debug output is to the (raw) console */
+                    fptr = header_fmt + strlen (header_fmt) - 1;    /*   then find the end of the string */
 
-                va_end (argptr);                                /* clean up the argument list */
+                    if (*fptr == '\n') {                /* if the format ends with a LF */
-                break;                                          /*   and exit with the job complete */
+                        *fptr++ = '\r';                 /*   then replace it */
+                        *fptr++ = '\n';                 /*     with a CR LF sequence */
+                        *fptr   = '\0';                 /*       and terminate with a NUL */
+                        }
+                    }
+
+                vfprintf (sim_deb, header_fmt, argptr); /* format and print to the debug stream */
+
+                va_end (argptr);                        /* clean up the argument list */
+                break;                                  /*   and exit with the job complete */
                 }
 
             else                                        /* otherwise */
@@ -3453,14 +3487,22 @@ return;
 }
 
 
-/* Make a pair of devices consistent */
+/* Make a pair of devices consistent.
+
+   Most of the disc and tape devices use two interface cards, designated the
+   command channel and the data channel.  These are simulated with two DEVICE
+   structures.  When a SET <dev> ENABLE or DISABLE command is directed to one of
+   the cards, the other chard wants to be set to the same state.  Calling this
+   routine with the target card as the first parameter and the other card as the
+   second parameter will do it.
+*/
 
 void hp_enbdis_pair (DEVICE *ccptr, DEVICE *dcptr)
 {
-if (ccptr->flags & DEV_DIS)
+if (ccptr->flags & DEV_DIS)                             /* if the target device is disabled */
-    dcptr->flags |= DEV_DIS;
+    dcptr->flags |= DEV_DIS;                            /*   then disable the other device */
-else
+else                                                    /* otherwise */
-    dcptr->flags &= ~DEV_DIS;
+    dcptr->flags &= ~DEV_DIS;                           /*   enable the other device */
 
 return;
 }
@@ -3547,12 +3589,13 @@ run_handler   = find_cmd ("RUN")->action;               /*   and the RUN/GO comm
 break_handler = find_cmd ("BREAK")->action;             /*     and the BREAK/NOBREAK command handler */
 load_handler  = find_cmd ("LOAD")->action;              /*       and the LOAD command handler */
 
+sim_vm_release        = hp_release;                     /* set up the release string */
 sim_vm_cmd            = aux_cmds;                       /* set up the auxiliary command table */
-sim_vm_fprint_stopped = fprint_stopped;                /* set up the simulation-stop printer */
+sim_vm_fprint_stopped = fprint_stopped;                 /* set up the simulation-stop printer */
-sim_vm_fprint_addr    = fprint_addr;                   /* set up the address printer */
+sim_vm_fprint_addr    = fprint_addr;                    /* set up the address printer */
-sim_vm_parse_addr     = parse_addr;                    /* set up the address parser */
+sim_vm_parse_addr     = parse_addr;                     /* set up the address parser */
-sim_vm_post           = cpu_post_cmd;                  /* set up the command post-processor */
+sim_vm_post           = cpu_post_cmd;                   /* set up the command post-processor */
-sim_vm_unit_name      = poll_name;                     /* set up the custom unit name handler */
+sim_vm_unit_name      = poll_name;                      /* set up the custom unit name handler */
 
 sim_brk_types = BP_SUPPORTED;                           /* register the supported breakpoint types */
 sim_brk_dflt  = BP_ENONE;                               /* the default breakpoint type is "execution" */

HP2100/hp2100_tty.c

@@ -1,7 +1,7 @@
 /* hp2100_tty.c: HP 12531C Buffered Teleprinter Interface simulator
 
    Copyright (c) 1993-2016, Robert M. Supnik
-   Copyright (c) 2017-2019, J. David Bryan
+   Copyright (c) 2017-2020, J. David Bryan
 
    Permission is hereby granted, free of charge, to any person obtaining a copy
    of this software and associated documentation files (the "Software"), to deal
@@ -26,6 +26,7 @@
 
    TTY          12531C Buffered Teleprinter Interface
 
+   25-Aug-20    JDB     Reset routine now sets up VM unit pointer hooks
    03-May-19    JDB     Output stall now doubles rescheduling wait
    26-Apr-19    JDB     Added "vm_console_[in/out]put_unit" declarations
    22-Sep-18    JDB     RESET -P now resets to original FASTTIME timing
@@ -276,9 +277,6 @@ static UNIT tty_unit [] = {
 #define print_unit          tty_unit [printer]  /* teleprinter printer unit */
 #define punch_unit          tty_unit [punch]    /* teleprinter punch unit */
 
-UNIT *vm_console_input_unit  = &key_unit;       /* console input unit pointer */
-UNIT *vm_console_output_unit = &print_unit;     /* console output unit pointer */
-
 
 /* Device information block */
 
@@ -576,7 +574,7 @@ return outbound;                                        /* return the outbound s
 /* TTY local SCP support routines */
 
 
-/* Set the keyboad input and print output filters.
+/* Set the keyboard input and print output filters.
 
    This validation routine is called to configure the character input filter for
    the keyboard unit and the output filter for the print unit.  The "value"
@@ -664,7 +662,7 @@ return SCPE_OK;                                         /* mode changes always s
    rejected; the unit must be detached first.  Otherwise, the device is disabled
    by setting the DEV_DIS flag.
 
-   In either case, the device is reset, which will restart or cancel the keyboad
+   In either case, the device is reset, which will restart or cancel the keyboard
    poll, as appropriate.
 */
 
@@ -728,6 +726,9 @@ if (sim_switches & SWMASK ('P')) {                      /* if this is a power-on
     tty.shift_in_data = MARK;                           /*     and preset the input shift register */
 
     fast_data_time = TTY_FAST_TIME;                     /* restore the initial fast data time */
+
+    vm_console_input_unit  = &key_unit;                 /* set up the console input */
+    vm_console_output_unit = &print_unit;               /*   and console output unit pointers */
     }
 
 if (tty_dev.flags & DEV_DIS)                            /* if the device is disabled */
@@ -843,7 +844,7 @@ if (tty.mode & CN_INPUT) {                              /* if the card is set fo
     io_assert (&tty_dev, ioa_ENF);                      /*   and the flag */
 
     if (tty.mode & (CN_PRINT | CN_PUNCH))               /* if the printer or punch is enabled */
-        status = output ((int32) input);                /*   then scho the received character */
+        status = output ((int32) input);                /*   then echo the received character */
     else                                                /* otherwise */
         status = SCPE_OK;                               /*    silently indicate success */
     }

doc/hp2100_release.txt

@@ -1,7 +1,7 @@
                            SIMH/HP 2100 RELEASE NOTES
                         ================================
                         J. David Bryan <jdbryan@acm.org>
-                             Last update: 2020-02-14
+                             Last update: 2020-11-07
 
 
 This file documents the release history of the simulator for the Hewlett-Packard
@@ -173,7 +173,7 @@ Manuals describing the operation of HP software are available from Bitsavers at:
 
 ...and from the HP Computer Museum at:
 
-  http://www.hpmuseum.net/collection_document.php
+  http://www.hpmuseum.net/collection_document.php#CS
 
 
 ----------------
@@ -221,6 +221,306 @@ Revision 5010:
 
 
 
+======================
+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=<n>
+   command restricts each process to executing <n> 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-<code>",
+   where <code> 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 <network-port> 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 <network-port>
+
+     ...command.  Line units are attached to serial ports with the:
+
+       ATTACH MUXL <serial-port>
+
+     ...command.  These behave as expected.  However, the:
+
+       ATTACH MUXL <network-port>
+
+     ...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
 ======================