Altair 8800 Simulator with Z80 support ====================================== 0. Revision History Original version of this document written by Charles E Owen - 4-May-2002, Peter Schorn (added description of MP/M II sample software) - 28-Apr-2002, Peter Schorn (added periodic timer interrupts and three additional consoles) - 15-Apr-2002, Peter Schorn (added memory breakpoint) - 7-Apr-2002, Peter Schorn (added ROM / NOROM switch) 1. Background. The MITS (Micro Instrumentation and Telemetry Systems) Altair 8800 was announced on the January 1975 cover of Popular Electronics, which boasted you could buy and build this powerful computer kit for only $397. The kit consisted at that time of only the parts to build a case, power supply, card cage (18 slots), CPU card, and memory card with 256 *bytes* of memory. Still, thousands were ordered within the first few months after the announcement, starting the personal computer revolution as we know it today. Many laugh at the small size of the that first kit, noting there were no peripherals and the 256 byte memory size. But the computer was an open system, and by 1977 MITS and many other small startups had added many expansion cards to make the Altair quite a respectable little computer. The "Altair Bus" that made this possible was soon called the S-100 Bus, later adopted as an industry standard, and eventually became the IEE-696 Bus. 2. Hardware We are simulating a fairly "loaded" Altair 8800 from about 1977, with the following configuration: device simulates name(s) CPU Altair 8800 with Intel 8080 CPU board, 62KB of RAM, 2K of EPROM with start boot ROM. SIO MITS 88-2SIO Dual Serial Interface Board. Port 1 is assumed to be connected to a serial "glass TTY" that is your terminal running the Simulator. PTR Paper Tape Reader attached to port 2 of the 2SIO board. PTP Paper Tape Punch attached to port 2 of the 2SIO board. This also doubles as a printer port. DSK MITS 88-DISK Floppy Disk controller with up to eight drives. 2.1 CPU We have 2 CPU options that were not present on the original machine but are useful in the simulator. We also allow you to select memory sizes, but be aware that some sample software requires the full 64K (i.e. CP/M) and the MITS Disk Basic and Altair DOS require about a minimum of 24K. SET CPU 8080 Simulates the 8080 CPU (normal) SET CPU Z80 Simulates the Z80 CPU. Note that some software (e.g. most original Altair software such as 4K Basic) requires an 8080 CPU and will not or not properly run on a Z80. This is mainly due to the use of the parity flag on the 8080 which has not always the same semantics on the Z80. SET CPU ITRAP Causes the simulator to halt if an invalid opcode is detected (depending on the chosen CPU). SET CPU NOITRAP Does not stop on an invalid Opcode. This is how the real 8080 works. SET CPU 4K SET CPU 8K SET CPU 12K SET CPU 16K ...... SET CPU 64K All these set various CPU memory configurations. The 2K EPROM at the high end of memory is always present and will always boot. SET CPU BANKED Enables the banked memory support. The simulated memory has four banks with address range 0..'common' (see registers below) and a common area from 'common' to 0xfff which is common to all banks. The currently active bank is determined by register 'bank' (see below). You can only switch to banked memory if the memory is set to 64K. The banked memory is used by CP/M 3. SET CPU NONBANKED Disables banked memory support. SET CPU ROM Enables the boot EPROM at address 0FF00H and prevents write access to the locations from 0FF00H to 0FFFFH. This is the default setting. SET CPU NOROM Disables the boot EPROM at address 0FF00H and enables write access to the locations from 0FF00H to 0FFFFH. The BOOT EPROM card starts at address 0FF00H. Jumping to this address will boot drive 0 of the floppy controller (CPU must be set to ROM or equivalent code must be present). If no valid bootable software is present there the machine crashes. This is historically accurate behavior. The real 8080, on receiving a HLT (Halt) instruction, freezes the processor and only an interrupt or CPU hardware reset will restore it. The simulator is alot nicer, it will halt but send you back to the simulator command line. CPU Registers include the following: name size comments PC 16 The Program Counter AF 16 The accumulator and the flag register F = S Z - AC - P/V N C S = Sign flag. Z = Zero Flag. AC = Auxillary Carry flag. P/V = Parity flag on 8080 Parity / Overflow flag on Z80 - = not used (undefined) N = Internal sign flag C = Carry flag. BC 16 The BC register pair. Register B is the high 8 bits, C is the lower 8 bits DE 16 The DE register pair. Register D is the high 8 bits, E is the lower 8 bits. HL 16 The HL register pair. Register H is the high 8 bits, L is the lower 8 bits. AF1 16 The alternate AF register (only on Z80) BC1 16 The alternate BC register (only on Z80) DE1 16 The alternate DE register (only on Z80) HL1 16 The alternate HL register (only on Z80) IX 16 The IX index register (only on Z80) IY 16 The IY index register (only on Z80) IFF 8 Interrupt flag (only on Z80, no effect) INT 8 Interrupt register (only on Z80, no effect) SR 16 The front panel switches (use D SR 8 for 4k Basic). WRU 8 The interrupt character. This starts as 5 (ctrl-E) but some Altair software uses this keystroke so best to change this to something exotic such as 035 (which is Ctl-]). BANK 3 The currently active memory bank (if banked memory is activated - see memory options above) COMMON 16 The starting address of common memory. Originally set to 0xc000 (note this setting must agree with the value supplied to GENCPM for CP/M 3 system generation) 2.2 The Serial I/O Card (2SIO) This simple programmed I/O device provides 2 serial ports to the outside world, which could be hardware jumpered to support RS-232 plugs or a TTY current loop interface. The standard I/O addresses assigned by MITS was 10-11 (hex) for the first port, and 12-13 (hex) for the second. We follow this standard in the Simulator. The simulator directs I/O to/from the first port to the screen. The second port reads from an attachable "tape reader" file on input, and writes to an attachable "punch file" on output. These files are considered a simple stream of 8-bit bytes. The SIO can be configured in SIMH with the following commands: SET SIO TTY Bit 8 is set to zero on console output SET SIO ANSI Bit 8 is not touched on console output SET SIO ALL Console input support lower- and upper case SET SIO UPPER Console input is transformed to upper case characters only (This feature is useful for most Altair software) SET SIO BS Map the delete character to backspace SET SIO DEL Map the backspace character to delete SET SIO QUIET Do not print warning messages SET SIO VERBOSE Print warning messages (useful for debugging) The register SIOWL determines how often the same warning is displayed. The default is 3. You can also attach the SIO to a port: ATTACH SIO 23 Console IO goes via a Telnet connection on port 23 DETACH SIO Console IO goes via the regular SIMH console 2.3 The SIMH pseudo device The SIMH pseudo device facilitates the communication between the simulated ALTAIR and the simulator environment. This device defines a number of (most R/O) registers (see source code) which are primarily useful for debugging purposes. The SIMH pseudo device can be configured with SET SIMH QUIET Do not print warning messages SET SIMH VERBOSE Print warning messages (useful for debugging) SET SIMH TIMERON Start periodic timer interrupts SET SIMH TIMEROFF Stop the periodic timer interrupts The following variables determine the behavior of the timer: TIMD This is the delay between consecutive interrupts in milliseconds. Use D TIMD 20 for a 50 Hz clock. TIMH This is the address of the interrupt handler to call for a timer interrupt. 2.4 The 88-DISK controller. The MITS 88-DISK is a simple programmed I/O interface to the MITS 8-inch floppy drive, which was basically a Pertec FD-400 with a power supply and buffer board builtin. The controller supports neither interrupts nor DMA, so floppy access required the sustained attention of the CPU. The standard I/O addresses were 8, 9, and 0A (hex), and we follow the standard. Details on controlling this hardware are in the altair_dsk.c source file. The only difference is that the simulated disks may be larger than the original ones: The original disk had 77 tracks while the simulated disks support up to 254 tracks (only relevant for CP/M). For debugging purposes you can set the trace level of some disk I/O functions. To do so the following bits in TRACE (a register of the disk) have been defined with the following meaning: 1 Trace all IN and OUT instructions on the disk ports 8 and 9 2 Trace all read and writes to full sectors on the disk 4 Print a message whenever an unnecessary step-in or step out of the disk head occurs (often an indication of an infinite loop) 8 Print a message whenever the disk head appears to be waiting for a sector which does not show up (often an indication of an infinite loop) For example the command "D TRACE 10" will trace options 2+8 from above. The DSK device can be configured with SET DSK QUIET Do not print warning messages for disk SET DSK VERBOSE Print warning messages for disk (useful for debugging) The register DSKWL determines how often the same warning is displayed. The default is 3. SET DSK WRITEENABLED Allow write operations for disk SET DSK LOCKED Disk is locked, i.e. no write operations will be allowed. 3. Sample Software Running an Altair in 1977 you would be running either MITS Disk Extended BASIC, or the brand new and sexy CP/M Operating System from Digital Research. Or possibly, you ordered Altair DOS back when it was promised in 1975, and are still waiting for it to be delivered in early 1977. We have samples of all three for you to check out. We can't go into the details of how they work, but we'll give you a few hints. 3.1 CP/M Version 2.2 This version is my own port of the standard CP/M to the Altair. There were some "official" versions but I don't have them. None were endorsed or sold by MITS to my knowledge, however. To boot CP/M: sim> attach dsk cpm2.dsk sim> boot dsk CP/M feels like DOS, sort of. DIR will work. I have included all the standard CP/M utilities, plus a few common public-domain ones. I also include the sources to the customized BIOS and some other small programs. TYPE will print an ASCII file. DUMP will dump a binary one. LS is a better DIR than DIR. ASM will assemble .ASM files to Hex, LOAD will "load" them to binary format (.COM). ED is a simple editor, #A command will bring the source file to the buffer, T command will "type" lines, L will move lines, E exits the editor. 20L20T will move down 20 lines, and type 20. Very DECish. DDT is the debugger, DO is a batch-type command processor. A sample batch file that will assemble and write out the bootable CP/M image (on drive A) is "SYSCPM2.SUB". To run it, type "DO SYSCPM2". In order to efficiently transfer files into the CP/M environment use the included program R . If you have a file named foo.ext in the current directory (i.e. the directory where SIMH is), executing R FOO.EXT under CP/M will transfer the file onto the CP/M disk. Transferring a file from the CP/M environment to the SIMH environment is accomplished by W . The disk "cpm2.dsk" contains the following files: Name Ext Size Comment ASM .COM 8K ; CP/M assembler BDOS .MAC 66K ; Basic Disk Operating System assembler source code BOOT .COM 1K ; transfer control to boot ROM BOOT .MAC 2K ; source for BOOT.COM BOOTGEN .COM 2K ; put a program on the boot sectors CBIOSX .MAC 10K ; CP/M 2 BIOS source for Altair CCP .MAC 26K ; Console Command Processor assembler source code COPY .COM 1K ; copy disks CPMBOOT .COM 12K ; CP/M operating system CREF80 .COM 4K ; cross reference utility DDT .COM 5K ; 8080 debugger DDTZ .COM 10K ; Z80 debugger DIF .COM 3K ; determine differences between two files DO .COM 2K ; batch processing DSKBOOT .COM 1K ; code for boot ROM DSKBOOT .MAC 3K ; source for boot ROM DUMP .COM 1K ; hex dump a file ED .COM 7K ; line editor ELIZA .BAS 9K ; Elisa game in Basic EX8080 .COM 9K ; exercise 8080 instruction set EX8080 .MAC 47K ; source for EX8080.COM EX8080 .SUB 1K ; benchmark execution of EX8080.COM EXZ80 .COM 9K ; exercise Z80 instruction set EXZ80 .MAC 47K ; source for EXZ80.COM EXZ80 .SUB 1K ; benchmark execution of EXZ80.COM FORMAT .COM 2K ; format disks GO .COM 0K ; start the currently loaded program at 100H L80 .COM 11K ; Microsoft linker LADDER .COM 40K ; game LADDER .DAT 1K ; high score file for LADDER.COM LIB80 .COM 6K ; library utility LOAD .COM 2K ; load hex files LS .COM 3K ; directory utility LU .COM 20K ; library utility M80 .COM 20K ; Microsoft macro assembler MBASIC .COM 24K ; Microsoft Basic interpreter MC .SUB 1K ; assemble and link an assmbler program MCC .SUB 1K ; read, assemble and link an assmbler program MOVER .MAC 2K ; moves operating system in place OTHELLO .COM 12K ; Othello (Reversi) game PIP .COM 8K ; Peripheral Interchange Program R .COM 3K ; read files from SIMH environment RSETSIMH.COM 1K ; reset SIMH interface RSETSIMH.MAC 1K ; assembler source for RSETSIMH.COM SHOWSEC .COM 3K ; show sectors on a disk SID .COM 8K ; debugger for 8080 STAT .COM 6K ; provide information about currently logged disks SURVEY .COM 2K ; system survey SURVEY .MAC 15K ; assembler source for SURVEY.COM SYSCOPY .COM 2K ; copy system tracks between disks SYSCPM2 .SUB 1K ; create CP/M 2 on drive A: TSHOW .COM 1K ; show split time TSHOW .MAC 1K ; assembler source for TSHOW.COM TSTART .COM 1K ; create timer and start it TSTART .MAC 1K ; assembler source for TSTART.COM TSTOP .COM 1K ; show final time and stop timer TSTOP .MAC 1K ; assembler source for TSTOP.COM UNCR .COM 7K ; un-crunch utility UNERA .COM 2K ; un-erase a file UNERA .MAC 16K ; source for UNERA.COM USQ .COM 2K ; un-squeeze utility W .COM 3K ; write files to SIMH environment WM .COM 11K ; word master screen editor WM .HLP 3K ; help file for WM.COM WORM .COM 4K ; worm game for VT100 terminal XSUB .COM 1K ; support for DO.COM ZSID .COM 10K ; debugger for Z80 ZTRAN4 .COM 4K ; translate 8080 mnemonics into Z80 equivalents 3.2 CP/M Version 3 with banked memory CP/M 3 is the successor to CP/M 2.2. A customised BIOS (BIOS3.MAC) is included to facilitate modification if so desired. The defaults supplied in GENCPM.DAT for system generation can be used. BOOTGEN.COM is used to place the CP/M loader (LDR.COM) on the boot tracks of a disk. Running CP/M 3 with banked memory: sim> attach dsk cpm3.dsk sim> reset cpu sim> set cpu banked sim> set cpu itrap sim> boot dsk Executing "DO SYSCPM3" will re-generate the banked version of CP/M 3. You can boot CP/M 3 with or without a Z80 CPU. The Z80 CPU is needed for both sysgens due to the use of BOOTGEN.COM which requires it. The disk "cpm3.dsk" contains the following files: ASM .COM 8K ; CP/M assembler ASSIGN .SYS 2K BDOS3 .SPR 10K BIOS3 .MAC 28K ; CP/M 3 BIOS source for Altair SIMH BIOS3 .SPR 4K BNKBDOS3.SPR 14K BNKBIOS3.SPR 4K BOOT .COM 2K ; transfer control to boot ROM BOOTGEN .COM 2K ; put a program on the boot sectors CCP .COM 4K COPYSYS .COM 2K CPM3 .SYS 18K CPMLDR .MAC 38K ; CP/M 3 loader assembler source DATE .COM 4K ; date utility DDT .COM 6K ; 8080 debugger DDTZ .COM 10K ; Z80 debugger DEFS .LIB 2K ; include file for BIOS3.MAC to create banked CP/M 3 DEVICE .COM 8K DIF .COM 4K ; determine differences between two files DIR .COM 16K ; directory utility DO .COM 6K ; batch processing DUMP .COM 2K ED .COM 10K ERASE .COM 4K GENCOM .COM 16K GENCPM .COM 22K GENCPM .DAT 4K ; CP/M generation information for banked version GENCPMNB.DAT 4K ; CP/M generation information for non-banked version GET .COM 8K HELP .COM 8K ; help utility HELP .HLP 62K ; help files HEXCOM .CPM 2K HIST .UTL 2K INITDIR .COM 32K L80 .COM 12K ; Microsoft linker LDR .COM 4K ; CP/M loader with optimised loader BIOS LDRBIOS3.MAC 14K ; optimised (for space) loader BIOS LIB .COM 8K ; Digital Research librarian LINK .COM 16K ; Digital Research linker LOAD .COM 2K M80 .COM 20K ; Microsoft macro assembler MC .SUB 2K ; assemble and link an assmbler program MCC .SUB 2K ; read, assemble and link an assembler program PATCH .COM 4K PIP .COM 10K ; Peripheral Interchange Program PROFILE .SUB 2K ; commands to be executed at start up PUT .COM 8K R .COM 4K ; read files from SIMH environment RENAME .COM 4K RESBDOS3.SPR 2K RMAC .COM 14K ; Digital Research macro assembler RSETSIMH.COM 2K ; reset SIMH interface SAVE .COM 2K SCB .MAC 2K SET .COM 12K SETDEF .COM 6K SHOW .COM 10K SHOWSEC .COM 4K ; show sectors on a disk SID .COM 8K ; 8080 debugger SYSCOPY .COM 2K ; copy system tracks between disks SYSCPM3 .SUB 2K ; create banked CP/M 3 system TRACE .UTL 2K TSHOW .COM 2K ; show split time TSTART .COM 2K ; create timer and start it TSTOP .COM 2K ; show final time and stop timer TYPE .COM 4K UNERA .COM 2K ; un-erase a file W .COM 4K ; write files to SIMH environment XREF .COM 16K ; cross reference utility ZSID .COM 10K ; Z80 debugger 3.3 MP/M II with banked memory MP/M II is an acronym for MultiProgramming Monitor Control Program for Microprocessors. It is a multiuser operating system for an eight bit microcomputer. MP/M II supports multiprogramming at each terminal. This version supports four terminals available via Telnet. To boot: sim> attach dsk mpm.dsk sim> set cpu itrap sim> set cpu z80 sim> set cpu rom sim> set cpu banked sim> attach sio 23 sim> boot dsk Now connect a Telnet session to the simulator and type "MPM" at the "A>" prompt. Now you can connect up to three additional terminals via Telnet to the Altair running MP/M II. To re-generate the system perform "DO SYSMPM" in the CP/M environment (not possible under MP/M since XSUB is needed). The disk "mpm.dsk" contains the following files: Name Ext Size Comment ABORT .PRL 2K ; abort a process ABORT .RSP 2K ASM .PRL 10K ; MP/M assembler BNKBDOS .SPR 12K ; banked BDOS BNKXDOS .SPR 2K ; banked XDOS BNKXIOS .SPR 4K ; banked XIOS BOOTGEN .COM 2K ; copy an executable to the boot section CONSOLE .PRL 2K ; print console number CPM .COM 2K ; return to CP/M CPM .MAC 2K ; source for CPM.COM DDT .COM 6K ; MP/M DDT DDT2 .COM 6K ; CP/M DDT DDTZ .COM 10K ; CP/M DDT with Z80 support DIF .COM 4K ; difference between two files DIR .PRL 2K ; directory command DO .COM 2K ; CP/M submit DSKRESET.PRL 2K ; disk reset command DUMP .MAC 6K ; source for DUMP.PRL DUMP .PRL 2K ; dump command ED .PRL 10K ; MP/M line editor ERA .PRL 2K ; erase command ERAQ .PRL 4K ; erase comand (verbose) GENHEX .COM 2K GENMOD .COM 2K GENSYS .COM 10K L80 .COM 12K ; Microsoft linker LDRBIOS .MAC 14K ; loader BIOS LIB .COM 8K ; library utility LINK .COM 16K ; linker LOAD .COM 2K ; loader M80 .COM 20K ; Microsoft macro assembler MC .SUB 2K ; assemble and link an assmbler program MCC .SUB 2K ; read, assemble and link an assembler program MPM .COM 8K ; start MP/M II MPM .SYS 26K ; MP/M system file MPMD .LIB 2K ; define a banked system MPMLDR .COM 6K ; MP/M loader without LDRBIOS MPMSTAT .BRS 6K ; status of MP/M system MPMSTAT .PRL 6K MPMSTAT .RSP 2K MPMXIOS .MAC 26K ; XIOS for MP/M PIP .PRL 10K ; MP/M peripheral interchange program PIP2 .COM 8K ; CP/M peripheral interchange program PRINTER .PRL 2K PRLCOM .PRL 4K R .COM 4K ; read a file from the SIMH environment RDT .PRL 8K ; debugger for page relocatable programs REN .PRL 4K ; rename a file RESBDOS .SPR 4K ; non-banked BDOS RMAC .COM 14K ; Digital Research macro assembler RSETSIMH.COM 2K ; reset SIMH interface SCHED .BRS 2K ; schedule a job SCHED .PRL 4K SCHED .RSP 2K SDIR .PRL 18K ; fancy directory command SET .PRL 8K ; set parameters SHOW .PRL 8K ; show status of disks SPOOL .BRS 4K ; spool utility SPOOL .PRL 4K SPOOL .RSP 2K STAT .COM 6K ; CP/M stat command STAT .PRL 10K ; MP/M stat command STOPSPLR.PRL 2K ; stop spooler SUBMIT .PRL 6K ; MP/M submit SYSCOPY .COM 2K ; copy system tracks SYSMPM .SUB 2K ; do a system generation SYSTEM .DAT 2K ; default values for system generation TMP .SPR 2K TOD .PRL 4K ; time of day TSHOW .COM 2K ; show split time TSTART .COM 2K ; create timer and start it TSTOP .COM 2K ; show final time and stop timer TYPE .PRL 2K ; type a file on the screen USER .PRL 2K ; set user area W .COM 4K ; write a file to SIMH environment XDOS .SPR 10K ; XDOS XREF .COM 16K ; cross reference utility XSUB .COM 2K ; for CP/M DO 3.5 CP/M application software There is also a small collection of sample application software containing the following items: - SPL: a Small Programming Language with a suite of sample programs - PROLOGZ: a Prolog interpreter written in SPL with sources - PASCFORM: a Pascal pretty printer written in Pascal - Pascal MT+: Pascal language system needed to compile PASCFORM The sample software comes on "app.dsk" and to use it do sim> attach dsk1 app.dsk before booting CP/M. The disk "app.dsk" contains the following files: Name Ext Size Comment BOOTGEN .COM 2K BOOTGEN .SPL 6K ; SPL source for BOOTGEN.COM C .SUB 2K ; batch file for compiling an SPL source file CALC .PRO 4K ; Prolog demo program calculator CC .SUB 2K ; compile an SPL source which is on the underlying file system DECLARAT. 12K ; common include file, SPL source DIF .COM 4K DIF .SPL 10K ; SPL source for DIF.COM EDIT .SPL 10K ; screen editor for PROLOGZ, SPL source FAMILY .PRO 4K ; Prolog demo program family relations INTEGER .PRO 2K ; Prolog demo program integer arithmetic KNAKE .PRO 2K ; Prolog demo program logic puzzle LINKMT .COM 12K ; Pascal MT+ 5.5 linker MAIN .SPL 14K ; main module for PROLOGZ, SPL source MOVE .MAC 4K ; helper functions for PROLOGZ in assembler MTERRS .TXT 6K ; Pascal MT+ error messages MTPLUS .000 14K ; Pascal MT+ 5.5 compiler file MTPLUS .001 12K ; Pascal MT+ 5.5 compiler file MTPLUS .002 8K ; Pascal MT+ 5.5 compiler file MTPLUS .003 8K ; Pascal MT+ 5.5 compiler file MTPLUS .004 18K ; Pascal MT+ 5.5 compiler file MTPLUS .005 8K ; Pascal MT+ 5.5 compiler file MTPLUS .006 6K ; Pascal MT+ 5.5 compiler file MTPLUS .COM 36K ; Pascal MT+ 5.5 compiler PASCFORM.COM 36K ; Pascal formatter PASCFORM.PAS 54K ; Pascal formatter source code PASCFORM.SUB 2K ; create Pascal formatter PASLIB .ERL 24K ; Pascal MT+ 5.5 run time library PINST .COM 4K ; terminal installation program for PROLOGZ PINST .SPL 16K ; terminal installation program for PROLOGZ, SPL source PROLOGZ .COM 18K ; PROLOGZ interpreter and screen editor PROLOGZ .SPL 2K ; PROLOGZ main program, SPL source PROLOGZ .TXT 40K ; PROLOGZ documentation in German PROVE .SPL 16K ; backtrack theorem prover for PROLOGZ, SPL source PZCLEAN .SUB 2K ; PROLOGZ: remove all created ".rel" and ".lst" files PZLINK .SUB 2K ; PROLOGZ: create PINST, PROLOGZ and personalise the serial number PZMAKE .SUB 2K ; compiles the sources (you can ignore any compiler errors) QUEEN .PRO 2K ; Prolog demo program n-queens problem READ .COM 4K READ .SPL 10K ; SPL source for R.COM SHOWSEC .COM 4K SHOWSEC .SPL 6K ; SPL source for SHOWSEC.COM SPL .COM 38K ; the SPL compiler itself SPL .TXT 56K ; SPL language and compiler documentation in German SPLERROR.DAT 12K ; error messages of the compiler (in German) SPLIB .REL 6K ; SPL runtime library STDIO . 2K ; include file for SPL programs SYSCOPY .COM 2K SYSCOPY .SPL 6K ; SPL source for SYSCOPY.COM TERMBDOS.SPL 2K ; terminal interface to CP/M for PROLOGZ, SPL source UTIL .SPL 18K ; utility functions for PROLOGZ, SPL source WRITE .COM 4K WRITE .SPL 8K ; SPL source for W.COM 3.6 MITS Disk Extended BASIC Version 4.1 This was the commonly used software for serious users of the Altair computer. It is a powerful (but slow) BASIC with some extended commands to allow it to access and manage the disk. There was no operating system it ran under. To boot: sim> set cpu 8080 ;Z80 will not work sim> attach dsk mbasic.dsk sim> set sio upper sim> go ff00 MEMORY SIZE? [return] LINEPRINTER? [C return] HIGHEST DISK NUMBER? [0 return] (0 here = 1 drive system) NUMBER OF FILES? [3 return] NUMBER OF RANDOM FILES? [2 return] 44041 BYTES FREE ALTAIR BASIC REV. 4.1 [DISK EXTENDED VERSION] COPYRIGHT 1977 BY MITS INC. OK [MOUNT 0] OK [FILES] 3.7 Altair DOS Version 1.0 This was long promised but not delivered until it was almost irrelevant. A short attempted tour will reveal it to be a dog, far inferior to CP/M. To boot: sim> attach dsk altdos.dsk sim> set sio upper sim> go ff00 MEMORY SIZE? [return] INTERRUPTS? N [return] HIGHEST DISK NUMBER? [0 return] (3 here = 4 drive system) HOW MANY DISK FILES? [3 return] HOW MANY RANDOM FILES? [2 return] 056449 BYTES AVAILABLE DOS MONITOR VER 1.0 COPYRIGHT 1977 BY MITS INC .[MNT 0] .[DIR 0] 3.8 Altair Basic 3.2 (4k) In order to run the famous 4k Basic, use the following commands (the trick is to get the Switch Register right). sim> set cpu 8080 ;note 4k Basic will not run on a Z80 CPU sim> set sio upper ;4k Basic does not like lower case letters as input sim> set sio ansi ;4k Basic produces 8-bit output, strip to seven bits sim> d sr 8 ;good setting for the Switch Register sim> load 4kbas.bin 0 ;load it at 0 sim> go 0 ;and start it MEMORY SIZE? [return] TERMINAL WIDTH? [return] WANT SIN? [Y] 61911 BYTES FREE BASIC VERSION 3.2 [4K VERSION] OK 3.9 Altair 8k Basic Running 8k Basic follows the procedure for 4k Basic. sim> set cpu 8080 ;note 8k Basic will not run on a Z80 CPU sim> set sio upper ;8k Basic does not like lower case letters as input sim> set sio ansi ;8k Basic produces 8-bit output, strip to seven bits sim> d sr 8 ;good setting for the Switch Register sim> load 8kbas.bin 0 ;load it at 0 sim> go 0 ;and start it MEMORY SIZE? [A] WRITTEN FOR ROYALTIES BY MICRO-SOFT MEMORY SIZE? [return] TERMINAL WIDTH? [return] WANT SIN-COS-TAN-ATN? [Y] 58756 BYTES FREE ALTAIR BASIC REV. 4.0 [EIGHT-K VERSION] COPYRIGHT 1976 BY MITS INC. OK 3.10 Altair Basic 4.0 Execute the following commands to run Altair Extended Basic. sim> set sio upper ;Extended Basic does not like lower case letters as input sim> set sio ansi ;Extended Basic produces 8-bit output, strip to seven bits sim> d sr 8 ;good setting for the Switch Register sim> load exbas.bin 0 ;load it at 0 sim> go 0 ;and start it 16384 Bytes loaded at 0. MEMORY SIZE? [return] WANT SIN-COS-TAN-ATN? [Y] 50606 BYTES FREE ALTAIR BASIC REV. 4.0 [EXTENDED VERSION] COPYRIGHT 1977 BY MITS INC. OK 4. Special simulator features In addition to the regular SIMH features such as PC queue, breakpoints etc., this simulator supports memory access breakpoints. A memory access breakpoint is triggered when a pre-defined memory location is accessed (read, write or update). To set a memory location breakpoint enter sim> break -m Execution will stop whenever an operation accesses . Note that a memory access breakpoint is not triggered by fetching code from memory (this is the job of regular breakpoints). This feature has been implemented by using the typing facility of the SIMH breakpoints. 5. Brief summary of all major changes to the original Altair simulator - Full support for Z80. CP/M software requiring a Z80 CPU now runs properly. DDTZ and PROLOGZ are included for demonstration purposes. - Added banked memory support. - PC queue implemented. - Full assembler and dis-assembler support for Z80 and 8080 mnemonics. Depending on the current setting of the CPU, the appropriate mnemonics are used. - The BOOT ROM was changed to fully load the software from disk. The original code basically loaded a copy of itself from the disk and executed it. - ROM and memory size settings are now fully honored. This means that you cannot write into the ROM or outside the defined RAM (e.g. when the RAM size was truncated with the SET CPU commands). This feature allows programs which check for the size of available RAM to run properly (e.g. 4k Basic). In addition one can enable and disable the ROM which is useful in special cases (e.g. when testing a new version of the ROM). - The console can also be used via Telnet. This is useful when a terminal is needed which supports cursor control such as a VT100. PROLOGZ for example has a built-in screen editor which works under Telnet. - Simplified file exchange for CP/M. Using the READ program under CP/M one can easily import files into CP/M from the regular file system. Note that PIP does not work properly on non-text files on PTR. - The WRITE program can be used to transfer files from the CP/M environment to the regular environment (binary or ASCII transfer). - The last character read from PTR is always Control-Z (the EOF character for CP/M). This makes sure that PIP (Peripheral Interchange Program on CP/M) will terminate properly. - Fixed a bug in the BIOS warm boot routine which caused CP/M to crash. - Modified the BIOS for CP/M to support 8 disks. - Added CP/M 3 banked version as sample software - Changed from octal to hex - Made the DSK and SIO device more robust (previously malicious code could crash the simulator) - Added memory access break points - Added periodic timer interrupts (useful for MP/M) - Added additional consoles (useful for MP/M) - Added MP/M II banked version as sample software