Since you and @dougg3 have looked at this problem it would be helpful to have your understanding of a possible way to accomplish this. I am not a hardware guy but I am willing to get my hands dirty I just don’t want to make it more difficult or error prone that need be. I have the AMD AM28F020 chips (32x) and a rom flasher TL866 plus to flash the individual chips. I also have the SIMM socket donated from a PPC 7200? that I don’t mind removing from the system board. I have a concern that de-soldering the ROMs, soldering sockets and replacing the chips will create to large an opportunity to errors. If there is a way to flash the SIMMs all at once I would gladly to that.
Hi
@John Tucker! One thing I should point out is a project like this would be useful for more than just the ANS, because I believe the rest of the PowerPC series prior to the G3 shared the same pinout (although we'd want to make sure; we don't want to ruin any ANS machines!). So that could help with the concern about limited demand for such a project. I see a few options with pros and cons:
Option 1: create a replica PowerPC ROM DIMM PCB. Just make a carbon copy of Apple's design. By copying Apple's exact design, it would be compatible with the Flasher app and would be able to be reflashed in-system.
The challenge I foresee with this approach is that looking at the pictures that
@Performa450 posted above, there's not enough room to add PLCC sockets for all 16 chips. The chips are so close together! When I replicated Apple's Lobos Board ROM SIMM for Quadras, there was plenty of room to add sockets, so it was easy to create something that could be initially programmed using the TL866 or equivalent.
You could program all 16 chips ahead of time before soldering them to the board, but then if anything went wrong in the future, it would require desoldering to fix. That would be a little tricky unless someone cloned a "Flash Gordon" type board for the DIMMs, like what
@Jockelill described above with the PDS programmer, but for the PowerPC DIMMs instead.
If there's enough vertical space inside these machines, you could possibly make the board super tall and stagger the chips so there's room for sockets. It would look really silly, but it could work.
Option 2: ditch the AM28F020 chips altogether and use something modern with more capacity. It's probably feasible to fit a total of 8 PLCC sockets if the chips are 4 megabit instead of 2 megabit, still giving a total of 4 MB of ROM space. That would probably leave enough room to fit the sockets. It wouldn't be in-system programmable without hacking the Flasher app to recognize/erase/program the modern chips, but it would be easy (though tedious) to bootstrap and reprogram externally with a chip programmer.
It might even be better to follow some of the cooler modern approaches and focus on making it programmable through a USB port on the DIMM rather than in-system. So you would use a modern computer to program it. Makes it more expensive but then you don't need a programmer for it.
One thing to look out for with this approach is people have noticed that modern flash chips have crappy drive strength. I'm not sure if PLCC chips like the SST39SF040 are affected by that problem.
I don't know which option is best. Option 1 is definitely more true to the era because then you basically have the same board that Apple was using during development, and it would work with their tools. But unless someone makes an external programmer or figures out a clever way to fit 16 PLCC sockets on the board, it would be very hard to recover from a bad flash. Option 2 seems like it would be easier to get something working initially with sockets. The USB port would likely be a lot of work though.
There's a few brainstorming ideas for you! Unfortunately I just don't have the time to work on something like this right now, but it's definitely doable if someone has enough dedication!
, the idea was to make an adapter for the ROM SIMM Programmer that also could do the PPC ROMs, but at that time the biggest issue was us sourcing the necessary female slot connector (PPC ROM SIMM connector) for the adapter (yeah, stealing one from an old board could work, but wouldn't be very viable). Then life and other projects has kept us away from the concept 
