Macintosh SE ROM Adapter

[Bolle]

I was preparing a few Macs which I was going to sell today and stumbled across this SE with missing ROMs.

While looking for for replacements I only found 32pin 27s EPROMs in the spare parts box and those need some adaptation to work in the SE. I thought if I am going to do some adapter magic why not do it right and go for flash chips?

So I sat down and whipped this up:



That little adapter board will plug into the two ROM sockets on the logicboard and provide space for two PLCC32 flash chips.

Three additional address lines are exposed on the jumper header so you can go to 1MB of ROM using 29F040J and jumper the address lines to the CPU or the PDS slot.

A few questions remain though. Maybe someone who really knows what they are doing could chime in (hint: @bigmessowires )

/WR is also brought out to the header so you are able to connect it to R/W on the CPU and hopefully be able to use BMOWs flash tool to flash the ROMs from within the OS.

I am not yet totally sure if this would work though. I probably would have to modify the Flash tool to do more than 128KB at once or otherwise an interrupt between flashing chunks could destroy my ROMs.

Also the chips signature thing would likely have to be patched.

/CE and /OE are separate on the SE ROM sockets so I guess I do not need the inverter to make individual signals, correct?

 

[CC_333]

Oh, neat!

This could be like an extension for the ROMinator that BMoW built for the Plus (and presumably the 128k/512k(e) as well).

You could flash the SE SuperDrive ROMs on there, and then all one would need is the updated SWIM chip. Speaking of which, has anybody revere engineered that chip yet? I know BMoW got a good handle on the protocols used when creating the Floppy Emu, but for this to be a truly plug-and-play solution for upgrading an SE to SuperDrive standards, one would need to re-implement the SWIM chip using whatever the Floppy Emu uses. Not easy, I'd imagine.

The ROM is enough for now

c

 

[360alaska]

Neat, although I would suggest making the rom socket connections through-hole.

 

[Trash80toHP_Mini]

The "missing pins" for the ROM socket probably don't need to be implemented. Looks to me like that part of the "bus" would be the traces between the two PLCC32 flash chips.