The memory controller in the Quadra 650 is also used by the Q610 and Q800 (and Centris variants). I have none of these machines to verify with, but everymac.com says all of these machines max out at 32MB SIMMs.
I have no idea offhand if dougg3's ROM SIMM will work in these, but if anyone who has one of these is willing to solder a ROM SIMM socket on and test it out, it may (no promises, this is entirely early stages brainstorming) be possible to run 64MB SIMMs (or more hope than realism here, 128MB) in these with a ROM mod.
If anyone is up for it, and can confirm dougg3's ROM SIMM works in any of these machines, and has 64MB and 128MB SIMMs around to test with, let me know. It'd probably take me a couple days to come up with an initial patch, but it would be interesting to see if we could double or quadruple the usable RAM in these machines.
I have no idea offhand if dougg3's ROM SIMM will work in these, but if anyone who has one of these is willing to solder a ROM SIMM socket on and test it out, it may (no promises, this is entirely early stages brainstorming) be possible to run 64MB SIMMs (or more hope than realism here, 128MB) in these with a ROM mod.
If anyone is up for it, and can confirm dougg3's ROM SIMM works in any of these machines, and has 64MB and 128MB SIMMs around to test with, let me know. It'd probably take me a couple days to come up with an initial patch, but it would be interesting to see if we could double or quadruple the usable RAM in these machines.