Quadra 650 ROM Simm ...

I carefully desoldered the ROM socket from my Quadra 700 motherboard and soldered it into my Quadra 650 motherboard.

I also have a 2MB ROM SIMM module that I bought for my IIsi. It contains four M29F040-70 flash chips, so I can reprogram the chips ...

I'm now looking for a patched ROM for my Quadra 650 where the memory test is disabled and I can use four 128MB SIMM modules ...

How can I divide it into four sections? I suspect it will only result in four 256k sections, but I need four 512k sections. Can I simply fill them on the top with FF ...?

LL = low
UL = upper low
LU = lower high
UU = high

...is this correct?

I read that the ROM 2MB Modul I have (see the picture) is not Compatible with the Quadra ROM SIMM slot/socket ...? Have I to patch the Modul I have?

How do I need to patch my 2MB SE/30 ROM SIMM to be able to use it with the Q650?

I have a programmer for the 29F040 chips but I have to program each 29F040 individually.

Pin 11 (/CE) of the SIMM needs to be tied to 5V in order to disable the onboard ROMs. You should contact siliconinsider for details of how his ROM SIMM is wired as you will need to cut some traces. Presumably /CE on the SIMM connector is wired to /CE of the 4 flash chips; they would need to be disconnected from Pin 11 and tied low (asserted) or to /OE, whichever is easier.

Note that the Pin 11 /CE modification would need to be removed if the module were to be used in an earlier Mac II series system otherwise it will at a minimum not work and would likely damage things.

Alternatively you could cut some traces on the logic board to achieve a similar effect, but that would be nasty.

For most "correct" behavior you should duplicate each image twice when flashing to larger ROM chips but on the Quadra machines Apple does not make use of aliasing so leaving the unused spaced unprogrammed (0xFF) is fine. There are tools floating around that you can do the split with. Likewise for modified ROM images.

@dougg3 has an excellent write up here:

franklyn said:

I carefully desoldered the ROM socket from my Quadra 700 motherboard and soldered it into my Quadra 650 motherboard.

I also have a 2MB ROM SIMM module that I bought for my IIsi. It contains four M29F040-70 flash chips, so I can reprogram the chips ...

I'm now looking for a patched ROM for my Quadra 650 where the memory test is disabled and I can use four 128MB SIMM modules ...

How can I divide it into four sections? I suspect it will only result in four 256k sections, but I need four 512k sections. Can I simply fill them on the top with FF ...?

LL = low
UL = upper low
LU = lower high
UU = high

...is this correct?

I read that the ROM 2MB Modul I have (see the picture) is not Compatible with the Quadra ROM SIMM slot/socket ...? Have I to patch the Modul I have?

Click to expand...

I otherwise have ROMs here (Sweden) that work in the Quadra 650, can send it pre flashed.

Thank you both so much for all the tips ...

I'll first make a plan first of what needs to be patched on the SE/30 simm so that the simm works in the quadra.


I can buy a programmer and a 8MB Simm for 140,- Euro plus tax but I like to build it with parts i have already.

franklyn said:

Thank you both so much for all the tips ...

I'll first make a plan first of what needs to be patched on the SE/30 simm so that the simm works in the quadra.


I can buy a programmer and a 8MB Simm for 140,- Euro plus tax but I like to build it with parts i have already.

Click to expand...

Haha, yeah, that IS a fair point, another “easy way” is to lift rhe VCC legs on the onboard ROM chips. I did that on the 475 when I did the first development.

I will path the ROM Simm so the Q650 Mainboard are original.