xprt
Experienced Member
I thought some folks here might be interested in a hobby project I worked on and wrote up here:
http://mini-altair.tripod.com/
(Sorry for the ads.)
It's an 8085 single board computer intended to be compatible with the original Altair software.
It runs all the Altair BASICs: 4K, 8K, 12K Extended BASIC, Disk BASIC. It also runs Altair DOS and CP/M.
Instead of a ROM chip, I used a microcontroller to pre-load the RAM. The microcontroller can also do the functions of a front panel: examine and deposit to memory, jump to address and single step. I never added the lights and switches, however.
Something that may be unique is the SD card floppy emulator emulates the 88-DCDD floppy system, which allows it to run the Altair Disk BASICS and Altair DOS unmodified. It uses the FAT32 format so disk images can be transfered easily. It is basically just 3 chips: a microcontroller chip with a regulator and a buffer. This could easily be adapted to an S100 board.
Some may find it distasteful, but the board is a combination of some 1970s chips with modern flash programmable LSI chips. It is wirewrap construction with some fine pitch surface mount parts thrown in.
It was an interesting project. I found debugging the disk emulator to be quite challenging. Breakpoints don't work too well with multiple CPUs doing time-critical operations. I found myself disassembling the Disk BASIC code and running through it in my head to debug it.
Any questions, comments, criticisms are welcome.
http://mini-altair.tripod.com/
(Sorry for the ads.)
It's an 8085 single board computer intended to be compatible with the original Altair software.
It runs all the Altair BASICs: 4K, 8K, 12K Extended BASIC, Disk BASIC. It also runs Altair DOS and CP/M.
Instead of a ROM chip, I used a microcontroller to pre-load the RAM. The microcontroller can also do the functions of a front panel: examine and deposit to memory, jump to address and single step. I never added the lights and switches, however.
Something that may be unique is the SD card floppy emulator emulates the 88-DCDD floppy system, which allows it to run the Altair Disk BASICS and Altair DOS unmodified. It uses the FAT32 format so disk images can be transfered easily. It is basically just 3 chips: a microcontroller chip with a regulator and a buffer. This could easily be adapted to an S100 board.
Some may find it distasteful, but the board is a combination of some 1970s chips with modern flash programmable LSI chips. It is wirewrap construction with some fine pitch surface mount parts thrown in.
It was an interesting project. I found debugging the disk emulator to be quite challenging. Breakpoints don't work too well with multiple CPUs doing time-critical operations. I found myself disassembling the Disk BASIC code and running through it in my head to debug it.
Any questions, comments, criticisms are welcome.