In the author’s previous post, they discovered how to use Apple’s leaked Flasher utility from the 1990s to reflash a ROM SIMM in a Performa 630. They reverse-engineered the code and hardware to determine compatibility and figure out the purpose of the “PDS ROM Info” section. The PDS slot on Macs allows for expansion, such as Ethernet or a video card. The author wanted to get the PDS portion of the software working, so they disassembled the Flasher utility and researched classic Mac hardware and Motorola MC680x0 processors. They realized they needed to create a PDS card to program the Lobos board, and they decided to use an LC 475 for the experiment. They looked at the MC68020 user manual to understand the logic needed for the PDS card and used programmable logic to handle bus control and flash write/read cycles. The card was built on a protoboard, and basic testing showed that the design worked properly. The next step was connecting the PDS card to the ROM SIMM programmer board.
https://www.downtowndougbrown.com/2023/12/more-fun-with-apples-internal-tools-creating-a-pds-card/