macintosh rom simms

Brian Lanning brianlanning at
Tue Mar 10 13:33:01 CDT 2009

On Tue, Mar 10, 2009 at 1:26 PM, Jeff Walther <trag at> wrote:
> Every Macintosh from the II forward (well, probably not the Classic) was
> built with a ROM socket.   However, the vast majority of them have ROM
> chips soldered to the board, and the socket is only there for updates
> which were never deemed worthwhile.
> Unless you have an incredibly rare Q700, there are ROM chips soldered to
> the board.   They'll have a part number something like 343S0xxx or
> 341S0xxx and there will probably be four of them (each with its own,
> probably sequential, number), although there might only be two if they
> used 16 bit wide chips.  I'm not sure if the Q700 is recent enough, but at
> some point they moved to 44 pin PSOPs for almost all their soldered down
> ROMs.
> Symptom of a missing ROM would be that the machine powers up just fine and
> all the drives spin up, lights come on, but there is no start-up bong and
> never any video from the monitor output.   If the machine fails to power
> up all-together, then you have a different issue than lack of ROM.
> If you have a power supply failure, the power supplies from the IIcx,
> IIci, IIvi, IIvx, Q700, Centris 650, Q650, and PowerMac 7100 will work in
> the Q700.  It was a long-lived power supply model.

Thanks for the info.  Maybe I should just try to turn it on.  :-)

What's up with the two different types of simm socket for ram?  The
machine has 4 simms in the smaller (30 pin?) sockets and none in the
larger (72-pin?) sockets.  Can I put memory in both of them, is it one
or the other?


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