I have an older Macbook, specifically this model, and when I am upgrading the standard 1GB that it came with. I bought DDR2 667 PNY Memory - 2 X 2GB. According to those specs, my unit can manage 4GB. I called Apple just to verify and they told me the same thing.
When I put both sticks into the unit, the machine doesn't boot up.
When I take out one, and put in the old 512MB, it boots up fine and when I get into OS X it tells me I have 2.5GB of RAM (which is right).
I have tried both sticks in both slots (all the possible combinations with the two original 512MB sticks). All combinations work (i.e. 2GB A with 512MB A, 2GB A with 512MB B, 2GB B & 512MB A and 2GB B & 512MB B), except with the 2 x 2GB.
Why is that?
I can't remember with certainty, but I think just the 2GB stick alone (with nothing in the other slot) does NOT work.
I am running memtest now on one of the sticks, to see if there is anything wrong with the actual sticks, so will update this once I have those results (could be a few hours though).
Any thoughts on what may be causing this and how I can fix it?
P.S. The PNY sticks are brand new.