First post, by pentiumspeed
These SIMM have IBM made chips in group of 9 chips of 4 bits each all identical to make parity of 36 bits wide. No matter what I set the sense detect pins correctly (Industry or IBM) I kept getting error right away during memory test POST on this compaq Deskpro 4/33i. Even set to 4MB 80ns with these IBM sticks still produces error. Exchange them all out for another correctly designed SIMMs worked.
When I exchanged for any SIMMs they works listed:
8 x 4MB x 4 bits with 4 x 4mb 1bit
8 x 4MB x 4 bits with single 4MB x 4 bits of the quad CAS 24 pin IC
2x 4mb x 16bits with 4 x 4mb 1 bits
2x 4mb x 16bits with single 4mb x 4bits of the quad CAS 24 pin IC
4x 4MB x 8 bits with single 4mb 4 bit quad CAS IC 24 pin IC
4x 4mb x 8 bits with 4x 4mb x 1 bit.
parity 72 pins modules requires 4 cas lines to work right especially for the four bit parity chips. that odd IBM made 4mb of 9 chips all same of 4 bits each does not work correctly. I was not happy that I have small collection of these I can not use.
This beyonds me how did IBM managed to able to use these in their IBM yet other SIMMs above will also work in theirs as well?!
Cheers,
Great Northern aka Canada.