> That is, could a person swap a 32 MB 72 pin SIMM out of
>a PC and put it in a Mac that uses 72 pin SIMMs (like the Q630 ;-)) Is
>there a rule of thumb as to what SIMMs will work with what sort of
>machine?
Ryan,
    Yes, I know of no problem with any of them that use the 72 pin SIMM.
And here, I've done it myself.  Like in either my Q605, a PC, or my 6116
or 7100/80.  I don't know of any "special requirement" for those 72 pin
types.  However, I have also had the opposite experience with older Mac's
that use 30 pin SIMMs; some are in some way quite unique, such as the 3
chip variety won't work in certain Mac's but will in others.  Things like
that.  Some 30 pin's that are parity SIMMs (9 chip) will work in some Macs
but give the tone of death on powerup on others.  Some Mac's, for whatever
reason, are sensitive to the actual chip organization used on the memory
array (the SIMMs matrix--ie, the row & column strategy used by the chip
matrix), I think it is, as the Apple TroubleShooting guide for some of
the older Mac's (I have one that ends with the IIvi I think it is) and 
they even point out SIMMs from certain vendors (and even date codes) that
simply won't work in certain Mac's, or give really strange addressing 
errors and so forth.  These are all 30 pin devices as I recall.  But, get
this, some of those that are troublesome in one Mac may actually work in
another model!  Those 3 chip SIMMs for example, may not work in a IIci 
but will run just peachy keen in an old SE30!!!  I know, I've experienced
that one right here myself!
Its pretty bizarre!

Paul