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mirror of https://github.com/PDP-10/its.git synced 2026-04-10 23:11:03 +00:00

Remove duplicate files SYSEN2; MLDEV 103 and KSHACK; KSDEFS 193.

It could be that KSHACK was the offial home for KSDEFS, but I think KS ITS
has moved from the hack stage and deserves its place in SYSTEM.
This commit is contained in:
Lars Brinkhoff
2017-02-17 11:12:59 +01:00
committed by Eric Swenson
parent 1b7ff86cdc
commit 24ced84164
5 changed files with 4 additions and 1987 deletions

720
src/kshack/mtboot.177 Executable file
View File

@@ -0,0 +1,720 @@
; -*- Mode:MIDAS -*-
TITLE MTBOOT - Create KS10 bootload tape or file.
;CStacy, 21 July 1984
;(Munged by Alan a great deal since then.)
; The 8080 front-end reads a tape starting with an optional
; microcode file, and EOF, and a 512 word bootload program
; which is loaded at 1000 and started.
;
; MTBOOT writes a file (to be copied onto a KS10 boot tape after the
; microcode file) containing the SBLK-bootstrap loader followed by SBLK
; files concatenated. Usually the first one is DDT and the second is
; some client program.
;
; OR
;
; MTBOOT will directly write a tape containing a microcode and the boot
; file.
;;; MTBOOT gets DDT from the file DSK:KSHACK;DDT BIN
;;; MTBOOT gets microcode from the file DSK:KSHACK;GOOD RAM
IFNDEF $$DBG, $$DBG==0 ;Set for debugging version of bootloader.
IFNDEF $$TPDBG, $$TPDBG==0 ;Set for debugging tape handling
IFNDEF $$SBDBG, $$SBDBG==0 ;Set for debugging SBLK stuff
SUBTTL Definitions
X=0 ;Super temporary.
A=1 ;A-E general purpose.
B=2
C=3
D=4
E=5
BP=6 ;Buffer pointer.
F=7 ;Flags.
RETRY=10 ;Count disk ops.
Q=11 ;Checksum.
T=12 ;Temporary ACs.
TT=13
P=17 ;Stack pointer.
; I/O channels for MTBOOT
DSKI==1 ;Disk input
OUTCH==2 ;Disk or tape output
TYIC==3 ;Typein
TYOC==4 ;Typeout
CALL==:<PUSHJ P,>
RET==:<POPJ P,>
NOP=:<TRN>
;System call macro
DEFINE SYSCAL OP,ARGS
.CALL [ SETZ ? SIXBIT /OP/ ? ARGS ((SETZ)) ]
TERMIN
;Canonical information macro.
DEFINE INFORM A,B
IF1,[ PRINTX /A = B
/]
TERMIN
;Type out an ascii string.
DEFINE TSTYPE &STRING
MOVEI T,<.LENGTH STRING>
MOVE TT,[440700,,[ASCII STRING]]
SYSCAL SIOT,[%CLIMM,,TYOC ? TT ? T]
.LOSE %LSFIL
TERMIN
;Type string from BP until null encountered.
DEFINE TYPEBP BPTR
MOVE T,BPTR
ILDB TT,T
JUMPE TT,.+3
.IOT TYOC,TT
JRST .-3
TERMIN
;Decrement ASCII byte pointer.
DEFINE DECBP C ;Decrement byte pointer.
ADD C,[70000,,] ;Back up the byte pointer.
SKIPGE C ;Did we cross a word boundary?
SUB C,[430000,,1] ; then fix it.
TERMIN
SUBTTL Main Program and Data
SYSLOS: .VALUE [ASCIZ ":Losage."]
JRST .-1
POPJ1: AOS (P) ;Canonical Skip
CPOPJ: POPJ P, ;Return.
DIE: .LOGOUT 1, ;JRST here to die.
MTBOOT: MOVE P,[-PDLLEN,,PDL-1] ;Init our stack.
PUSHJ P,RFN"RMNAME ;Find name of this machine.
SYSCAL OPEN,[%CLBIT,,<.UAO+%TJDIS> ? %CLIMM,,TYOC ? [SIXBIT /TTY/]]
.LOSE %LSFIL
SYSCAL OPEN,[%CLBIT,,.UAI ? %CLIMM,,TYIC ? [SIXBIT /TTY/]]
.LOSE %LSFIL
SYSCAL CNSGET,[%CLIMM,,TYIC ? %CLOUT,,X ? %CLOUT,,X ;Get TTY caps.
%CLOUT,,X ? %CLOUT,,X ? %CLOUT,,TTYOPT]
.LOSE %LSFIL
.SUSET [.RSNAME,,A]
MOVEM A,INFILE+3
MOVEM A,KSBOOT+3
TSTYPE "AKS10 ITS Bootload Generator."
SETZM MAGP
TSTYPE "AWrite a tape? "
PUSHJ P,YORNP
JRST NOTAPE
SETOM MAGP
TSTYPE "ARewind tape first? "
PUSHJ P,YORNP
JRST NOWIND
SYSCAL OPEN,[ [.BII,,OUTCH] ; Can only rewind in input mode...
[SIXBIT /MT0/]]
.LOSE %LSFIL
MOVE A,[OUTCH,,[1,,1]] ; rewind once
.MTAPE A,
.LOSE %LSSYS
NOWIND: SYSCAL OPEN,[ [1000+.BIO,,OUTCH] ; 1000 word records
[SIXBIT /MT0/]]
.LOSE %LSFIL
TSTYPE "AWriting microcode from "
MOVEI B,RAMFIL
MOVE D,[440700,,TYPEIN]
PUSHJ P,RFN"PFN
MOVE D,[440700,,TYPEIN]
TYPEBP D
PUSHJ P,COPY
MOVE A,[OUTCH,,[1,,5]] ; EOF once
.MTAPE A,
.LOSE %LSSYS
NOTAPE: TSTYPE "AInclude DDT? "
SETOM DDTP ;Normally we write DDT
SETOM PRGP ;and some other program.
PUSHJ P,YORNP
SETZM DDTP ;Say not to include DDT.
TSTYPE "AInput file (just press Return if none)? "
PUSHJ P,READER ;Read file name string.
CAIA
JRST [ MOVE D,[440700,,TYPEIN] ;Bp to the filename string.
MOVEI B,INFILE ;Ptr to file block.
PUSHJ P,RFN"RFN ;Parse the file name.
JRST MERGE ]
SETZM PRGP
SKIPN DDTP
JRST [ TSTYPE "AWriting just the loader is useless!"
JRST DIE ]
MERGE: SKIPE MAGP
JRST MERGE0
MOVEI A,KSBOOT ;Open the output file.
SYSCAL OPEN,[%CLBIT,,.BIO ? %CLIMM,,OUTCH ? 0(A) ? 1(A) ? 2(A) ? 3(A)]
.LOSE %LSFIL
MERGE0: TSTYPE "AWriting 512 word bootstrap loader."
MOVE A,[-1000,,PREBOOT] ;Pointer to bootload program.
.IOT OUTCH,A ;Write out 512 words.
SKIPN DDTP
JRST [ CALL MNSBLK
JRST MERGE1]
TSTYPE "AWriting DDT from "
MOVEI B,DDTBIN
MOVE D,[440700,,TYPEIN]
PUSHJ P,RFN"PFN
MOVE D,[440700,,TYPEIN]
TYPEBP D
PUSHJ P,COPY ;Write out DDT.
MERGE1: SKIPN PRGP
JRST [ CALL MNSBLK
JRST MERGE2]
SETOM CLIENP
TSTYPE "AWriting SBLK program from "
MOVEI B,INFILE
MOVE D,[440700,,TYPEIN]
PUSHJ P,RFN"PFN
MOVE D,[440700,,TYPEIN]
TYPEBP D
PUSHJ P,COPY ;Write out program.
MERGE2: SKIPE MAGP
JRST MERGE3
SYSCAL RFNAME,[%CLIMM,,OUTCH ? %CLOUT,,KSBOOT
%CLOUT,,KSBOOT+1 ? %CLOUT,,KSBOOT+2 ? %CLOUT,,KSBOOT+3]
.LOSE %LSFIL
TSTYPE "AWrote file "
MOVEI B,KSBOOT
MOVE D,[440700,,TYPEIN]
PUSHJ P,RFN"PFN
MOVE D,[440700,,TYPEIN]
TYPEBP D
MERGE3: .CLOSE OUTCH,
JRST DIE
;;; Open, gobble, and write out the file specified by B.
COPY: PUSH P,A
PUSH P,B
PUSH P,C
SYSCAL OPEN,[%CLBIT,,.BII ? %CLIMM,,DSKI ? 0(B) ? 1(B) ? 2(B) ? 3(B)]
.LOSE %LSFIL
JRST COPY1
COPY2: MOVE B,[-1000,,BUFFER]
.IOT OUTCH,B ;Copy out buffer.
COPY1: SETZM BUFFER ;Freshen buffer.
MOVE C,[BUFFER,,BUFFER+1]
BLT C,BUFFER+1000
MOVE A,[-1000,,BUFFER] ;Pointer to input buffer
.IOT DSKI,A ;Read max 512 words from file.
CAME A,[-1000,,BUFFER] ; Stop at EOF
JRST COPY2
.CLOSE DSKI,
POP P,C
POP P,B
POP P,A
RET
;;; Write minimum SBLK file:
MNSBLK: PUSH P,A
MOVE A,[-3,,[
JRST 1
JRST 4,17
JRST 4,17
]]
.IOT OUTCH,A
SETZM BUFFER
MOVE A,[BUFFER,,BUFFER+1]
BLT A,BUFFER+1000
MOVE A,[-775,,BUFFER]
.IOT OUTCH,A
POP P,A
RET
;;; Read from TYIC with minimal rubout handling (displays only).
;;; Uses TYPEIN buffer and skips if read something; returns count in A.
READER: MOVE BP,[440700,,TYPEIN]
SETZM TYPEIN ;Clear typein buffer.
MOVE A,[TYPEIN,,TYPEIN+1]
BLT A,TYPEIN+LTYPEI
SETZ A, ;Keep count in A.
READ1: .IOT TYIC,T
CAIN T,177 ;Rubout deletes chars.
JRST RUBOUT
CAIN T,^D ;^D rubs out a line.
JRST RUBALL
CAIE T,^C ;^C and ^M finish input.
CAIN T,^M
JRST [ MOVEI T,0
IDPB T,BP ;Tie off ASCIZ string.
SKIPE A ;If we read something
AOS (P) ; Skip
POPJ P, ] ; Return.
AOS A ;Keep count of chars read.
CAILE C,LTYPEI*5. ;Avoid overflowing the buffer.
JRST RUBALL
IDPB T,BP ;Stuff it.
CAIGE T,40 ;No random ctl chars allowed!
JRST [ .IOT TYOC,[^G]
JRST RUBOUT ]
JRST READ1 ;Get another.
RUBALL: TSTYPE " XXX?"
JRST READER ;Flush entire line.
RUBOUT: SKIPN A ;Something to rubout?
JRST [ .IOT TYOC,[^G] ; No, just beep.
JRST READ1 ]
MOVE T,TTYOPT ;Examine terminal.
TLNE T,%TOERS
JRST [ TSTYPE "X" ;If able, erase from screen
JRST RUBOU1 ]
LDB T,BP ;Else just echo deleted char.
.IOT TYOC,T
RUBOU1: DECBP BP
SOS A
JRST READ1
;;; Y-OR-N-P, skips for Yes.
YORNP: TSTYPE / (Y or N) /
.IOT TYIC,T
CAIN T,40 ;A [SPACE] means yes.
JRST POPJ1
CAIN T,177 ;A [RUBOUT] means no.
POPJ P,
CAIL T,140
SUBI T,40 ;Y or N mean the obvious.
CAIN T,"Y
JRST POPJ1
CAIN T,"N
POPJ P,
.IOT TYOC,[^G]
JRST YORNP ;Maybe obvious not to everybody????
$$RFN==1
$$PFN==1
$$MNAME==1
.INSRT DSK:SYSENG;RFN
RSIXTP:: ;Filename parser routines.
PSIXTP: POPJ P, ;No special character processing.
;;; Data
PDLLEN==200
LTYPEI==20.
LBUFFE==1001
TTYOPT: 0 ;TTYOPT word.
MAGP: 0 ;-1 if writing a tape.
DDTP: 0 ;-1 if DDT being written too.
PRGP: 0 ;-1 if program to "merge" with DDT.
CLIENP: 0 ;-1 if hacking client now.
MNAME: 0 ;Name of this ITS.
PDL: BLOCK PDLLEN ;Stack.
BUFFER: BLOCK 1001 ;Disk buffer.
TYPEIN: BLOCK LTYPEI+1 ;Typein buffer.
;;; File names.
KSBOOT: SIXBIT /DSK/
SIXBIT /KSBOOT/
SIXBIT />/
0
INFILE: SIXBIT /DSK/
SIXBIT /FOO/
SIXBIT /BIN/
0
DDTBIN: SIXBIT /DSK/
SIXBIT /DDT/
SIXBIT /BIN/
SIXBIT /KSHACK/
RAMFIL: SIXBIT /DSK/
SIXBIT /GOOD/
SIXBIT /RAM/
SIXBIT /KSHACK/
CONSTANTS
SUBTTL SBLK Bootstrap Loader
.INSRT SYSTEM;KSDEFS
MEMSIZ=1000000 ;The size of memory.
DDT=MEMSIZ-4000 ;Address of DDT.
JOBSYM=DDT-1 ;-1 if following is invalid.
; DDT-2 ;All symbols ptr.
KILC= DDT-3 ;Initial symbols ptr.
STARTA=DDT-4 ;Start address.
;Print a string
DEFINE TYPE &STRING
MOVEI T,[ASCIZ STRING]
CALL TYPOUT
TERMIN
;Type a SIXBIT value
DEFINE 6TYPE LOC
MOVEI T,LOC
CALL TYPSIX
TERMIN
;Type a number.
DEFINE 8TYPE LOC
MOVE T,LOC
CALL OCTPNT
TERMIN
;Type a CRLF (sugar macro).
DEFINE TYPECR
CALL CRLF
TERMIN
; Type character immediate.
DEFINE CTYPE CHAR
MOVEI TT,CHAR
CALL TYO
TERMIN
;Fatal error macro.
DEFINE ERROR &MSG
JRST [ MOVEI T,[ASCIZ MSG]
JSR BARF ]
TERMIN
; 1000 --- Start Program
; 1001 --- Lossage PC stored here.
; LOSE --- Horrible PC here.
IFNDEF ORG, ORG==:1000 ;Location of this bootload program in core (PREBOOT).
PREBOOT:
OFFSET ORG-.
JRST GO ;Go for it!.
BARF: 0 ;Errors JSR here
TYPECR
CALL TYPOUT
TYPECR
JRST 4,@BARF
LOSE: 0 ;Really awful errors JSR here.
JRST 4,@LOSE
IFN 0,[
IORD X,MTCS1 ;Store some I/O info in 103-113.
MOVEM X,103 ;MTCS1.
IORD X,MTCS2
MOVEM X,104 ;MTCS2.
IORD X,MTDS
MOVEM X,105 ;MTDS.
IORD X,MTER
MOVEM X,106 ;MTER1.
SETZM 107 ;Not used.
SETZM 110 ;Not used.
IORD X,IOPAGR
MOVEM X,111 ;UBA page RAM loc 0.
IORD X,IOSTAT
MOVEM X,112 ;UBA status register.
MOVE X,VERSUN
MOVEM X,113 ;Version of this bootloader.
];IFN 0
GO: ;; Clear core above and below the loader. Be careful about 8RHBAS
;; through 8BOOTP.
SETZM ORG+1000
MOVE A,[ORG+1000,,ORG+1001]
BLT A,777677 ; Don't clobber DSKDMP bootstrap
SETZM 8BOOTP+1
MOVE A,[8BOOTP+1,,8BOOTP+2]
BLT A,ORG-1
SETZM 20
MOVE A,[20,,21]
BLT A,8RHBAS-1
;; Clear all AC's and select block 0
CLRACS: WRUBR ACBLK+0 ; A in block 0 contains count.
MOVEI A,7 ; Start with block 7.
CLRACL: WRUBR ACBLK(A) ; Select next block
SETZI 0,
MOVEI 17,1
BLT 17,17 ; Clears A iff A already contained 0.
WRUBR ACBLK+0 ; Select block 0 again
SOJGE A,CLRACL ; Go do next?
MOVE P,[-LBOOPD,,BOOPDL-1] ;Init our stack.
MAKIOT: SKIPN A,8RHBAS ;Find 19 bit base addr of tape boot device.
ERROR "RH11 base?"
HLLM A,IOPAGR ;UBA pager this bus.
HLLM A,IOSTAT ;UBA status this bus.
MOVE B,[-NIOWDS,,MTCS1] ;AOBJN to IO words.
MAKIO1: MOVEM A,(B) ;Store unibus addr of tape control register.
ADDI A,2 ;Compute next one.
AOBJN B,MAKIO1 ;Go store them all.
HERALD: TYPE "ITS MTBOOT."
6TYPE VERSUN
SETZI BP, ; Buffer starts empty.
CALL LODCOD
MOVEM A,START
JRST LOAD3
LOAD4: CALL LODSKP
LOAD3: CALL MTIOT
JUMPL A,LOAD4
CAME A,START
ERROR "Start instruction mismatch"
CALL LODCOD
EXCH A,START ; Consider running second program
CAMN A,[JRST 4,17] ; Was first file the minimal SBLK file?
JRST DONE ; Yes: Run second program
EXCH A,START ; OK, so run first program
MOVE B,JOBSYM
CAIE B,DDT-2 ; Does it look like DDT?
JRST DONE ; No: Just go run it
MOVEM A,STARTA ; This must be DDT, set starting address
TLO B,400000
MOVEM B,JOBSYM ; and mark symbol table as clobbered
JRST LOAD5
LOAD6: CALL LODSYM
LOAD5: CALL MTIOT
JUMPL A,LOAD6
CAME A,STARTA
ERROR "Start instruction mismatch"
DONE: ;; Clear out loader and start him up.
SETZM ORG
MOVE 15,[ORG,,ORG+1] ; Load AC for BLT.
MOVE 16,[BLT 15,ORG+1777] ; This instruction does the work.
MOVE 17,START ; This is the start instruction.
JRST 16 ; Do it.
;;; Load a symbol table block or other information block. Enter with first
;;; word already in A.
;;; Clobbers A, B, C and Q.
LODSYM: HRRZ C,A ; C: type of block
JUMPN C,LODSKP
HLRE B,A
ADD B,A
ADDB B,@JOBSYM
HLL B,A
JRST LODBK1
;;; Skip over an information block. Enter with first word already in A.
;;; Clobbers A, B and Q.
LODSKP: MOVE B,A ; B: aobjn into hyperspace
MOVE Q,A ; Q: checksum
SKPLUP: ROT Q,1
CALL MTIOT
ADD Q,A
AOBJN B,SKPLUP
JRST CHKSUM
;;; Load the code from an SBLK file, returns start instruction in A.
;;; Clobbers A, B, C and Q.
LODCOD: CALL MTIOT ; Get a word
CAME A,[JRST 1] ; End of RDIN cruft?
JRST LODCOD ; No: keep looking.
JRST LODCD1
LODCD2: CALL LODBLK ; Loop loading SBLKs
LODCD1: CALL MTIOT
JUMPL A,LODCD2 ; Until start instruction
RET
;;; Load an SBLK into memory. Enter with first word already in A.
;;; Clobbers A, B, C and Q.
LODBLK: MOVE B,A ; B: aobjn into core
LODBK1: MOVE Q,A ; Q: checksum
LODLUP: ROT Q,1
HRRZ C,B ; C: destination address
CAIL C,8SWIT0 ; Smashing 8080 area?
CAILE C,8QNUM
CAIA
ERROR "Overwriting 8080 area"
CAIGE C,20 ; Smashing ACs?
ERROR "Overwriting ACs"
CAIL C,ORG ; Smashing loader?
CAILE C,ORG+1777
CAIA
ERROR "Overwriting loader"
CALL MTIOT ;Get word.
MOVEM A,(B) ;Store it.
ADD Q,A ;Do sum checking.
AOBJN B,LODLUP
CHKSUM: CALL MTIOT ;Read checksum.
CAME A,Q ;Match?
ERROR "Checksum error"
RET
; Get word from tape (or refill buffer) into A.
MTIOT: JUMPL BP,MTIOT1 ;Jump if buffer contains data
IFN $$TPDBG,CTYPE "%
MOVEI RETRY,20. ;Retry count
READ: CALL MTHAK ;Init tape.
MOVEI A,40001+<org/1000> ;Page after loader, UBA valid.
IOWR A,IOPAGR ;Map Unibus locations 0-1777 to KS10 mem.
SETZ A,
IOWR A,MTBA
MOVNI A,2000 ;2000 18-bit words = 1000 36-bit words.
IOWR A,MTWC
MOVEI A,71 ;Read forward
IOWR A,MTCS1
CALL IOWAIT
TRNE A,4 ;Premature tape mark?
ERROR "Unexpected EOF" ; Lose.
IORD A,MTER
TRNE A,176777 ;Tape error--retry
JRST [ SOJL RETRY,[ ERROR "Tape err" ]
CALL MTHAK
MOVNI A,1 ;Backspace one record.
IOWR A,MTFC
MOVEI A,33
IOWR A,MTCS1
CALL IOWAIT
JRST READ ]
MOVSI BP,-1000 ;Buffer contains data now
IFN $$TPDBG,CTYPE "$
MTIOT1: MOVE A,2000(BP) ;Get next word from buffer
AOBJN BP,.+1 ;Advance buffer pointer
IFN $$SBDBG,[
TYPE "... "
8TYPE A
MOVEI B,40000. ;Pause about 1/4 sec.
SOJG B,.
]; $$SBDBG
RET
MTHAK: IFN $$TPDBG,CTYPE "#
MOVEI A,40 ;Hack the tape drive.
IOWR A,MTCS2
MOVE A,8QNUM
IOWR A,MTCS2
MOVE A,8BOOTP
IOWR A,MTTC
SETZ A,
IOWR A,MTFC
RET
IOWAIT: IORD A,MTDS ;Wait for IO completion.
TRNN A,20000 ;Wait if positioning in progress
TRNN A,200 ;Wait until drive ready
JRST IOWAIT
RET
;Hand TT to 8080 for printing.
TYO: ANDI TT,177 ;Remove crap.
TRO TT,400 ;Set CTY-character-pending
MOVEM TT,8CTYOT ;Store in comm area
CONI TT ;Read 8080
TRO TT,80INT ;Hey you! Get this!
CONO (TT) ;Interrupt 8080
SKIPE 8CTYOT ;Wait for completion
JRST .-1
RET
IFN 0,[
;Wait for console char TT from the 8080.
TYI: SKIPN TT,8CTYIN ;Chars stored here by 8080.
RET
SETZM 8CTYIN ;Remember to clear it.
ANDI TT,177 ;Remove crap.
RET
]; 0
;Type Newline.
CRLF: MOVEI TT,15
CALL TYO
MOVEI TT,12
CALL TYO
RET
;Type SIXBIT from T.
TYPSIX: HRLI T,440600
MOVEI X,6
TYPSI1: ILDB TT,T
JUMPE TT,TYPSIZ
ADDI TT,40
CALL TYO
SOJG X,TYPSI1
TYPSIZ: RET
;Type ASCIZ from T.
TYPOUT: HRLI T,440700
TYPOUL: ILDB TT,T
JUMPE TT,TYPOUZ
CALL TYO
JRST TYPOUL
TYPOUZ: RET
;Type octal number from T.
OCTPNT: SETZ TT,
LSHC T,-3 ;shift instead of IDIVI, don't forget
LSH TT,-41 ;negative!
PUSH P,TT ;push remainder
SKIPE T ;done?
CALL OCTPNT ;no compute next one
OCTPN1: POP P,TT ;yes, take out in opposite order
ADDI TT,60 ;make ascii
CALL TYO
RET ;and return for the next one.
;;; WRUBR ACBLK+N selects AC block N as current and previous.
ACBLK: REPEAT 8, <400000+<1100*.RPCNT>>,,0
; Data
LBOOPD==20.
VERSUN: .FNAM2 ; Loader version.
BOOPDL: BLOCK LBOOPD ; The stack.
START: 0 ; Start instruction.
;;; Table of I/O addresses
MTCS1: 0
MTWC: 0
MTBA: 0
MTFC: 0
MTCS2: 0
MTDS: 0
MTER: 0
MTAS: 0
MTCK: 0
MTDB: 0
MTMR: 0
MTDT: 0
MTSN: 0
MTTC: 0
NIOWDS==:.-MTCS1
IOPAGR: UBAPAG
IOSTAT: UBASTA
VARIABLES
CONSTANTS
IF1,[ PRINTX /
Bootstrap loader /
.TYO6 .FNAM2 ]
INFORM [, length]\.-1000
IFG .-2000, .FATAL Bootstrap loader doesn't fit in 512 words.
BLOCK 1000 ;Pad the loader.
-1 ;Force core to exist.
OFFSET 0
END MTBOOT