As a slight tangential aside - https://www.downtowndougbrown.com/programmable-mac-rom-simms/ and http://www.bigmessowires.com/mac-rom-inator-ii/
Wonder if something like this is adaptable for later ROM SIMMs....
For now I'm planning to lay out a DIMM reader, but I also have in mind to modify my DIMM design a little so that something similar to Doug's programmer can work on it.
The thing is, these DIMMs are 64 bits wide. Unless the chips on board can be addressed/activated-for-programming one or two at a time, it will get complicated.
On my list of things to do is looking at Doug's design to see if he set it up to program all four chips at once, or one or two at a time.
The thing about Doug's and Rob's work though is that they synergized very nicely. They both happened to be looking at their respective things at the same time. Rob was looking at how to modify some low level things (memory max, startup sounds, RAM disks, bootable ROM images - like the Classic has onboard) and Doug was looking at creating a custom ROM module for the older machines. It may have been Doug who was looking at sound originally. I can't remember any more.
I think it started with someone pulling the IIci ROMs and replacing them with sockets and programmable chips. The work was tracked, as it happened, in a very long thread on this forum, way back when.
But the two sets of work dovetailed with each other and luckily occurred in the same time frame.
There's not really, as far as I can tell, anyone chomping at the bit to modify firmware in the X100 through Beige era machines. At least, not yet. The closest thing is Cheesestraws work on fixing PCI-PCI Bridge support in the Gazelle and maybe the Alchemy boards.
I would like a fix for PCI-PCI bridges in the Umax S900, but that machine doesn't have a ROM slot. Modifying/replacing the four soldered down chips are the only choice on that machine.
Anyway, all that said, it still couldn't hurt to have a programmable ROM module for the whole family of machines. It sure looks like the modules used in the PEx machines are programmable modules -- whether they are programmable while installed in th3 PEx or require some special rig that lived at Apple, I don't know. But they use EEPROM chips and appear to have the Vpp pins wired up, which suggests an intent to reprogram the module.
@jimjamyahauk Why don't you send me your shipping address in PM, or email (firstname.lastname@example.org). jt will be shipping a couple of what we hope are the Digibarn copies back to me in the next week or two, and then I'll ship them on to you.