PAL SIMMs...
I read the desciption somewhere once, but I can't remember where. Maybe in one of Apple's reference manuals, such as GTTMFH. So I'm not very helpful, but from what little I recall, the PAL SIMMs massage one or more of the control lines in some way.
Regarding your 2 MB SIMMs with PALs on board:
PAL simply stands for Programmable Array Logic. PALs are a type of PLD and are very versatile.
So, while Apple called SIMMs with a PAL on board to provide the specific function which the IIx needed, "PAL SIMMs", not every SIMM with a PAL on board, has that particular special logic for the IIx implemented.
In the case of your 2 MB SIMMs, they're really like a pair of two-chip 1 MB SIMMs on the same board. The PAL decodes the address and directs the lower half of the addresses to one 1 MB SIMM and directs the upper half of the addresses to the other 1 MB SIMM. But there's no reason to believe that the PAL decoding the addresses for the 2 MB SIMM also implements the logic that the IIx needs.
I wish I could remember what that was... Maybe something to do with refresh and RAS and CAS?
I read the desciption somewhere once, but I can't remember where. Maybe in one of Apple's reference manuals, such as GTTMFH. So I'm not very helpful, but from what little I recall, the PAL SIMMs massage one or more of the control lines in some way.
Regarding your 2 MB SIMMs with PALs on board:
PAL simply stands for Programmable Array Logic. PALs are a type of PLD and are very versatile.
So, while Apple called SIMMs with a PAL on board to provide the specific function which the IIx needed, "PAL SIMMs", not every SIMM with a PAL on board, has that particular special logic for the IIx implemented.
In the case of your 2 MB SIMMs, they're really like a pair of two-chip 1 MB SIMMs on the same board. The PAL decodes the address and directs the lower half of the addresses to one 1 MB SIMM and directs the upper half of the addresses to the other 1 MB SIMM. But there's no reason to believe that the PAL decoding the addresses for the 2 MB SIMM also implements the logic that the IIx needs.
I wish I could remember what that was... Maybe something to do with refresh and RAS and CAS?