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simh-testsetgenerator/AltairZ80/altairZ80.txt
Bob Supnik 701f0fe028 Notes For V2.8 
1. New Features

1.1 Directory and documentation

- Only common files (SCP and libraries) are in the top level
  directory.  Individual simulator files are in their individual
  directories.
- simh_doc.txt has been split up.  simh_doc.txt now documents
  only SCP.  The individual simulators are documented in separate
  text files in their own directories.
- mingw_build.bat is a batch file for the MINGW/gcc environment
  that will build all the simulators, assuming the root directory
  structure is at c:\sim.
- Makefile is a UNIX make file for the gcc environment that will
  build all the simulators, assuming the root directory is at
  c:\sim.

1.2 SCP

- DO <file name> executes the SCP commands in the specified file.
- Replicated registers in unit structures can now be declared as
  arrays for examine, modify, save, and restore.  Most replicated
  unit registers (for example, mag tape position registers) have
  been changed to arrays.
- The ADD/REMOVE commands have been replaced by SET unit ONLINE
  and SET unit OFFLINE, respectively.
- Register names that are unique within an entire simulator do
  not have to be prefaced with the device name.
- The ATTACH command can attach files read only, either under
  user option (-r), or because the attached file is ready only.
- The SET/SHOW capabilities have been extended.  New forms include:

	SET <dev> param{=value}{ param ...}
	SET <unit> param{=value}{ param ...}
	SHOW <dev> {param param ...}
	SHOW <unit> {param param ...}

- Multiple breakpoints have been implemented.  Breakpoints are
  set/cleared/displayed by:

	BREAK addr_list{[count]}
	NOBREAK addr_list
	SHOW BREAK addr_list

1.3 PDP-11 simulator

- Unibus map implemented, with 22b RP controller (URH70) or 18b
  RP controller (URH11) (in debug).
- All DMA peripherals rewritten to use map.
- Many peripherals modified for source sharing with VAX.
- RQDX3 implemented.
- Bugs fixed in RK11 and RL11 write check.

1.4 PDP-10 simulator

- ITS 1-proceed implemented.
- Bugs fixed in ITS PC sampling and LPMR

1.5 18b PDP simulator

- Interrupts split out to multiple levels to allow easier
  expansion.

1.5 IBM System 3 Simulator

- Written by Charles (Dutch) Owen.

1.6 VAX Simulator (in debug)

- Simulates MicroVAX 3800 (KA655) with 16MB-64MB memory, RQDX3,
  RLV12, TSV11, DZV11, LPV11, PCV11.
- CDROM capability has been added to the RQDX3, to allow testing
  with VMS hobbyist images.

1.7 SDS 940 Simulator (not tested)

- Simulates SDS 940, 16K-64K memory, fixed and moving head
  disk, magtape, line printer, console.

1.8 Altair Z80

- Revised from Charles (Dutch) Owen's original by Peter Schorn.
- MITS 8080 with full Z80 simulation.
- 4K and 8K BASIC packages, Prolog package.

1.9 Interdata

The I4 simulator has been withdrawn for major rework.  Look for
a complete 16b/32b Interdata simulator sometime next year.

2. Release Notes

2.1 SCP

SCP now allows replicated registers in unit structures to be
modelled as arrays.  All replicated register declarations have
been replaced by register array declarations.  As a result,
save files from prior revisions will generate errors after
restoring main memory.

2.2 PDP-11

The Unibus map code is in debug.  The map was implemented primarily
to allow source sharing with the VAX, which requires a DMA map.
DMA devices work correctly with the Unibus map disabled.

The RQDX3 simulator has run a complete RSTS/E SYSGEN, with multiple
drives, and booted the completed system from scratch.

2.3 VAX

The VAX simulator will run the boot code up to the >>> prompt.  It
can successfully process a SHOW DEVICE command.  It runs the HCORE
instruction diagnostic.  It can boot the hobbyist CD through SYSBOOT
and through the date/time dialog and restore the hobbyist CD, using
standalone backup.  On the boot of the restored disk, it gets to the
date/time dialog, and then crashes.

2.4 SDS 940

The SDS 940 is untested, awaiting real code.

2.5 GCC Optimization

At -O2 and above, GCC does not correctly compile the simulators which
use setjmp-longjmp (PDP-11, PDP-10, VAX).  A working hypothesis is
that optimized state maintained in registers is being used in the
setjmp processing routine.  On the PDP-11 and PDP-10, all of this
state has been either made global, or volatile, to encourage GCC to
keep the state up to date in memory.  The VAX is still vulnerable.

3. Work list

3.1 SCP

- Better ENABLE/DISABLE.

3.2 PDP-11 RQDX3

Software mapped mode, RCT read simulation, VMS debug.
2011-04-15 08:33:38 -07:00

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Altair 8800 Simulator
=====================
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.
The BOOT EPROM card starts at address FF00. Jumping to this address
will always boot drive 0 of the floppy controller. 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-]).
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
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 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.
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 altcpm.dsk
sim> go ff00
62K CP/M VERSION 2.2 (ALTAIR 8800)
A>DIR
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, SUBMIT 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 "SYSGEN.SUB". To run it, type "SUBMIT SYSGEN".
In order to efficiently transfer files into the CP/M environment use the
included program READ <filename.ext>. If you have a file named foo.ext in
the current directory (i.e. the directory where SIMH is), executing
READ FOO.EXT under CP/M will transfer the file onto the CP/M disk. READ will
only run with Z80 CPU so remember to "SET CPU Z80".
The disk "altcpm.dsk" contains the following files:
Name Ext Size Comment
ABOOT62 ASM 1K Moves CP/M image from MOVCPM location to real location
in memory
ASM COM 8K Standard CP/M assembler
CALC PRO 3K Prolog sample file "Calculator"
CBIOS ASM 8K BIOS for the Altair (used for sysgen)
COPY COM 1K ALTAIR diskette backup program
CPM62 COM 9K CP/M binary (used for sysgen)
DDT COM 5K Dynamic Debugging Tool (Standard CP/M)
DDTZ COM 10K Dynamic Debugging Tool for Z80
DUMP ASM 5K Assembler source for DUMP utility
DUMP COM 1K Dumps the contents of a file in hex (Standard CP/M)
ED COM 7K Line oriented editor (Standard CP/M)
FAMILY PRO 2K Prolog sample file "Family relations"
FORMAT COM 2K Formats a disk
INTEGER PRO 1K Prolog sample file "Integer arithmetic"
KNAKE PRO 2K Prolog sample file "Logic puzzle"
LOAD COM 2K Loads a hex file and produces an executable
(Standard CP/M)
LS COM 3K Directory utility
MOVCPM COM 12K Regenerates the CP/M system for a particular
memory size (Standard CP/M)
PINST COM 4K Terminal installer for PROLOGZ.COM
PIP COM 8K Peripheral Interchange Program for copying files
(Standard CP/M)
PROLOGZ COM 17K Prolog development environment
PROLOGZ TXT 40K PROLOGZ documentation in German
PTD ASM 2K Writes Altair-format memory image to disk
(used for sysgen)
QUEEN PRO 2K Prolog sample file "N Queens problem"
READ COM 2K Reads a file from the SIMH filesystem to CP/M
README TXT 3K This file
STAT COM 6K Provides information about drives, disks and
files (Standard CP/M)
SUBMIT COM 2K Submits a file of commands for batch processing
(Standard CP/M)
SURVEY COM 2K Provides information about memory and IO ports
SYSCOPY COM 2K Copies the reserved tracks between disks
SYSGEN SUB 2K Submit file for generating the CP/M system
XSUB COM 2K Addition to SUBMIT such that all input is read
from the submit file (Standard CP/M)
3.2 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] (3 here = 4 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
3.3 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
3.4 Altair 4k Basic
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 ;load it
sim> go ;and go
MEMORY SIZE? [return]
TERMINAL WIDTH? [return]
WANT SIN? [Y]
61911 BYTES FREE
BASIC VERSION 3.2
[4K VERSION]
OK
3.5 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 ;load it
sim> go ;and go
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
4. 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.
- 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).
- 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 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.
- Changed from octal to hex which is more concise.
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