Brain Board

A ROM card for the Apple II that can, among other things, enable Apple I compatibility:

https://www.willegal.net/appleii/brainboard.htm

So far, the gerbers available at the link have been imported into a KiCad 9 PCB file. There is a ground fix that needs to be applied in the rework:

https://www.willegal.net/blog/?p=1880

The schematic also needs to be reverse-engineered. (There is a schematic in the manual, but it's of such low resolution that it will likely be of questionable utility.)