MPU-A-ROM

[bhall66]

I've spent the past few weeks hand disassembling the IMSAI ROM hex file. It is about 1000 lines of code. Before I post it and embarrass myself, does anyone have original & commented source code for this ROM?

Bruce.

[bhall66]

I have a follow up question: does anyone know which board and/or system this ROM belonged to? Even though the filename implies an MPU-A board, the features in this ROM (serial port, parallel keyboard input, F3 control port, timers, etc) all speak to it being installed on an MPU-B board. Was it for a PCS-80/30, a VDP-80, or something else?

[bhall66]

I just posted my disassemblies to https://github.com/bhall66/IMSAI-8080/tree/main/roms.

The file labelled "MPU-A-ROM" seems meant for an MPU-B board, as does "MPU-B-ROM". I am not certain, however, which came first. The monitor in A omits the cassette commands seen in B and A supports more disk controller types. In addition, a piece of working code found in B is orphaned (present but not used) in A. So, it is entirely possible that A came after B. Or, at least, it was meant for system that operated differently (a business computer, for example, that did not use cassette tapes). What do you think?

[udo-munk]

I was never able to find the original commented source, that probably is lost.
Also it is unknown from which systems the ROM images were dumped, the filenames were mpu-a.hex and mpu-b.hex already when I got them. Maybe they meant version A and version B of the ROM.