2-chip/3-chip 1MB RAM sticks in a Macintosh SE?

[GRudolf94]

1MB ones are all gonna be 1024 rows, yes. That is a factor of the number of bits needed to address that amount of memory. How many chips a SIMM30 module has is a factor of how many bits are in each chip - 8/9 in the case of one bit per chip, plus a parity bit (so 41256 type chips and similar), and two chips when each chip can hold 4 bits like happens with the 44256, plus the adjacent, optional (and in the mac unused) parity chip.
I don't think it's a test mode thing. The SE/Classic are not a Mac II family machine, either - more so their own thing, but still original Mac-derived.

It'd be interesting to have part numbers of modules known to not work to compare against good ones.

 

[Phipli]

You're right that with a square layout, 1024 rows are needed for 1MB SIMMS.

8/9-chip 1MB SIMMs must also have 1024 rows. Considering that, Apple's explanation is a bit puzzling:

https://www.tech-insider.org/mac/research/acrobat/9204.pdf

I think someone writing that either over simplified or stumbled on their words or something.

The only other plausible explanation in there I could find is that 4Mb chips introduced a JEDEC test mode that gets tripped on Mac IIs, but nothing is mentioned about the SE.

Might just be refresh frequency. Newer chips might like being refreshed more often, and it might be more common with 4bit word chips. I don't know though.