The Cortex A9 will be on all variants as it is included on a SoM that already has the FPGA system built-in. That said in the base configuration it wouldn't be used as it wouldn't include ADB loop-back and such, thus it would be cheaper. The problem is that the FPGA solution requires many I/O for the PDS. There is a pre-packaged board that will be attached to our PCB to use Xilinx XC7Z020 which has enough capability. This has 106 user I/Os which is what we need, also DAC is involved on the board. My goal is to have a Grayscale only card be around $350 and the Linux compatibility version be around $395. The benefit of a SoM is that future additions of Ethernet, USB, etc simply require FPGA update and Mac OS driver functionality. Since the final project will be be open source enough it will allow others to make the software side of things work.
Interesting project. So is the Cortex processor going to be present on all variants or is it an add-in sort of thing? Personally I'd only be interested in the grayscale adapter part; I wouldn't use most of the rest of it.
As for Ubuntu, has anyone tried to see how usable it would be at that resolution? Most modern installs give me fits if trying to run on anything under 1024x768@24bpp, so I can't imagine it would be happy with 512x384@8bpp.
PDSes were different from machine to machine, some with pass-throughs for additional signals such as sound and others having (or missing) lines to control cache or FPU presence. I don't think ADB was ever available at any PDS though. You'd probably have to build a Y-cable with one end going to the SE/30's ADB port and the other to your expansion card's ADB input which you could build into the external slot interface. It wouldn't ruin the aesthetic too much.
@OldMacGuy Your keyboard seems to have the same pull-out drawer as one of the other surviving Twiggy Macs. Is there anything inside?
Thanks for the additional pictures! I'm grateful you're taking the time to thoroughly photograph and document this machine.
Also, not really that related but I was reading an interesting journal article about Mac power consumption, here's the link: https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwiY3vXU9-HpAhVBa80KHZ2YCbQQFjACegQIARAB&url=http%3A%2F%2Fwww2.eecs.berkeley.edu%2FPubs%2FTechRpts%2F1997%2FCSD-97-961.pdf&usg=AOvVaw2pnD3j5sPvyVFtO7xwtL4J