Some time ago, I sat down with a pile of RAM (32 MB, 64 MB and 128 MB SIMMs) and a pile of logic boards, Q605, Q610, Q650/800, Q840, PM6100, PM7100 and PM8100. I would have tested a Q630, I have a logic board, but I have no chassis/power supply for the Q630.
I published my results either at 68kmla.org or at Applefritter. However, that may have been before one of the system crashes that lost content at one or both sites...
Fortunately, I keep a lab notebook...
All of the SIMMs worked in the Q605. That's one versatile little machine.
The 32 MB SIMMs worked in all of the machines tested.
The 64 MB SIMMs:
Seen as 32 MB in the Q610 and Q650/800.
Seen as 16 MB in the Q840AV, PM7100 and PM8100.
Works in the PM6100.
The 128 MB SIMMs:
Seen as 64 MB in the Q610 and Q650/800.
Seen as 32 MB in the Q840AV, PM7100, PM8100.
Error Chime in the PM6100.
Reports are that the 128 MB SIMMs should work in the 6100 but mine didn't. However, the way that machines distinguish between banks on a SIMM is by wiring some of the RAS lines to one bank and other RAS lines to the other bank. Then the machine only activates the relevant RAS lines when it wishes to access a particular bank. In the PM 6100 there are four RAS lines which are tied together on the logic board in pairs. On these 128 MB SIMMs the four RAS lines are also tied together in pairs. But the pairs do not correspond. So I suspect that the problem is simply that the RAS lines on these SIMMs aren't wired in a way that is compatible with the way the PM6100 expects.
John, I'm not sure how to get a sticky made. I think you PM the site owner or a moderator -- do we have moderators?