Over the past several months, I've been designing and reverse-engineering a few boards for the Lisa and I can finally share my results now that I'm done.
First up, I made
replicas of the 2-port parallel card and the 2/5 motherboard that are as similar to the originals as possible. I actually put these on GitHub a month or so ago, but I realized that I forgot to make a post on here when I did!
After the intellectual property discussion on here about reverse-engineering the Sun SCSI card, I decided to just
make my own version that consolidates the glue logic into a GAL16V8 and that swaps the EPROM out for an F-RAM that can be reprogrammed without having to remove it from the Lisa. Hopefully that last feature makes it easy to write code for expansion cards! I originally wanted to use a 28C64 EEPROM instead of the F-RAM since they're a bit cheaper, but the write time of 5ms was just too slow.
For practice with 68K assembly, I also ended up
writing a little program that lets you write a 4K ROM image from your modern computer straight into the expansion card F-RAM over serial. It's really simple, but also really useful!
I also adapted this program to let you
load code straight into the Lisa's RAM over serial to speed up software development. It's sort of like the BLU serial bootstrap program, except that you don't have to hard-code the size of your program and it automatically jumps to your code after a one second timeout of not receiving any data from the serial port.
I'm not sure how useful some of these tools would be to people (the PCBs are probably way more useful than my assembly language programs), but I figured I'd share everything anyway.
Let me know how all this stuff looks and if you guys have any suggestions for potential future revisions!
