Zoom meeting Topic suggestion: How to rebuild/install CPM after a BIOS change

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Joseph Corda

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Mar 6, 2026, 11:07:31 PM (17 hours ago) Mar 6
to Altair 8800
Greetings
Looking for quick overview on the steps I need to rebuild(or patch) CP/M 2.2 and install in boot track after I have modified and assembled a new BIOS.  

As an example ..
I'm currently using Mike D's Serial CP/M 2.2 (see link below) and I would like to modify BIOSSER.ASM to support a Cromemco PRI card (Port J1 ports 53H/54H) for printing from CP/M.

Once BIOS is adjusted and assembled into a ROM/BIN file how do I do the following:
  • Take newly assembled BIOS and "patch" into the rest of CP/M
  • How to I get newly rebuilt/patched CP/M installed back onto boot track ?
  • Are there any different steps between using Serial CP/M and a disk based CP/M version?
Thanks
Joe 

Using Source from here:
https://deramp.com/downloads/altair/software/8_inch_floppy/CPM/CPM%202.2/Serial%20Disk%208Mb%20CPM%202.2%20(thru%2088-2SIO)/

Joseph Corda

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7:59 AM (8 hours ago) 7:59 AM
to Altair 8800
Ah...Never mind.. I should have read the BIOSSER.ASM file as Mike D spelled it out !

;    To patch changes made to this BIOS into a CP/M image saved from
;    MOVCPM (e.g., CPMxx.COM), use following commands:
;
;       A>DDT CPMxx.COM
;       -IBIOS.HEX
;       -Rxxxx      (where xxxx = BIAS computed below)
;       -G0         (Go zero, not "oh")
;       A>SYSGEN

Patrick Linstruth

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8:32 AM (8 hours ago) 8:32 AM
to Altair 8800
Yep, notes are at the top.

I just did this just the other day making a Serial CP/M for Interfacer 1.

Easy-PZ with the simulator.

There are some issues with using host serial ports with the Altair8800 (and probably AltairZ80). I am currently working on a complete re-write of that system.

SIMH makes it very difficult, if not impossible, to do anything above 9600 and not completely consume the host CPU.

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Peter Sterrantino

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11:00 AM (5 hours ago) 11:00 AM
to Patrick Linstruth, Altair 8800
Trying this myself for the modifications I made to the FDC Serial Server BIOS for the Interfacer 1. Following the comments, but the disk image in:
has 3 versions of MOVCPM. MOVCPM5, MOVCPM8, and MOVCPM8M. Which do I use? Thinking MOVCPM5 (as in CPM56.com), but not sure....

Pete

need to rebuild(or patch) CP/M 2.2 and install in boo

Patrick Linstruth

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11:24 AM (5 hours ago) 11:24 AM
to Altair 8800
That disk image you provided a link for should only have 1 version of MOVCPM on the image, which should be MOVCPM8S, which is the version of MOVCPM for the 8MB Serial CP/M.

MOVCPM8M is for the non-serial 8MB CP/M, MOVCPM5 should be for 5 inch disk images and MOVCPM for the original Altair 8” disk images.

56K CP/M 2.2b v1.0

For Altair 8Mb Serial Drive


A0>ls b:

Name    Ext Bytes   Name    Ext Bytes   Name    Ext Bytes   Name    Ext Bytes

AFORMAT COM    4K | DUMP    COM    4K | LS      COM    8K | STAT    COM    8K

ASM     COM    8K | ED      COM    8K | MOVCPM8SCOM   12K | SUBMIT  COM    4K

BIOS    ASM   64K | FINDBAD COM    4K | NSWP    COM   12K | SYSGEN  COM    4K

BOOT    ASM    8K | FORMAT8MCOM    4K | PCGET   COM    4K | WM      COM   12K

DDT     COM    8K | IOBYTE  TXT    4K | PCPUT   COM    4K | WM      HLP    4K

DUMP    ASM    8K | LOAD    COM    4K | PIP     COM    8K | XSUB    COM    4K

24 File(s), occupying 212K of 8168K total capacity

487 directory entries and 7956K bytes remain on B:

A0>


sim> show dsk

DSK     16 units

  DSK0  8978KB, attached to CPM22-8MB-56K.DSK, WRTENB

  DSK1  8978KB, attached to CPM22-8MBS-56K.DSK, WRTENB


Peter Sterrantino

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11:33 AM (4 hours ago) 11:33 AM
to Patrick Linstruth, Altair 8800
Not seeing  MOVCPM8S. Let me download everything again. I'm seeing this (63k?):

63K CP/M 2.2b v1.0

For Altair 8Mb Serial Drive

A0>DIR
A: ASM      SUB : ASM      COM : FORMAT8M COM : XSUB     COM
A: FORMAT   COM : LS       COM : DO       COM : LOAD     COM
A: IOBYTE   TXT : MAKEMOV  COM : MOVCPM5  COM : FINDBAD  COM
A: BIOS     ASM : MOVCPM8  COM : PIP      COM : STAT     COM
A: DDT      COM : R        COM : SYSGEN   COM : FORMAT8M ASM
A: W        COM : CPM56    COM : BOOT     ASM : CPM48    COM
A: MOVCPM8M COM : MBASIC   COM : BMOVCPM  COM : BIOS     PRN
A: BIOS     HEX : FORMAT8M PRN : FORMAT8M HEX
A0>LS B:

AFORMAT .COM   4k | DUMP    .COM   4k | LS      .COM   8k | STAT    .COM   8k
ASM     .COM   8k | ED      .COM   8k | MOVCPM8M.COM  12k | SUBMIT  .COM   4k
BIOS    .ASM  76k | FINDBAD .COM   4k | NSWP    .COM  12k | SYSGEN  .COM   4k
BOOT    .ASM  12k | FORMAT8M.COM   4k | PCGET   .COM   4k | WM      .COM  12k
DDT     .COM   8k | IOBYTE  .TXT   4k | PCPUT   .COM   4k | WM      .HLP   4k
DUMP    .ASM   8k | LOAD    .COM   4k | PIP     .COM   8k | XSUB    .COM   4k

B: 8168k   Used: 24/228k   Free: 486/7940k

A0>DIR MOVCPM*.*
A: MOVCPM5  COM : MOVCPM8  COM : MOVCPM8M COM

Pete

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