I know Apple calls for DDR2 PC2-6400 officially, but I have some PC2-4200 not being used - I was wondering if it would work? I can never remember the rules on RAM backwards compatibility. Any help is appreciated, Thank you!
No it cannot. Only install what is specified for your system.
Can you tell me why not? I was thinking the same thing the poster above you mentioned - that RAM was backwards compatible (as long as it's DDR2-DDR2, etc) but it would just run at the slower speed, obviously. I just didn't know if Apple had any restrictions on slower speeds or anything
Edit: Let me clarify: the iMac currently has no RAM. If I install this PC2-4200 stick, will it work? (I would just try it but don't have the iMac in my hands yet)