New RAM Issues

[XxThatSamGuyxX]

Okay so I changed the RAM in my year and a half old white MacBook... Everything seemed to go fine, then I turned the Mac on, the standby light came on but it didn't boot.
I changed back to the original DIMMs, and it booted completely normally.
I figured I might have loaded the new RAM wrong the first time, so I tried again. It still didn't boot. I put the original sticks back in and it was fine.

Should I be pressing some kind of key combination whilst booting after new memory, or leaving it longer than normal or something? Any ideas?

Cheers

 

[Alexwithad]

Is the new ram compatible with your mac?

 

[XxThatSamGuyxX]

I'm pretty sure it is... It matches with what System Profiler and the Crucial scanner told me I needed...

 

[Ryken]

your RAM could be defective

 

[Cave Man]

Put one old and one new chip in.

If it boots, then replace the one new one with the other new one. If it still boots, you bought incompatible RAM.

If it doesn't boot with either of the new chips paired with an old chip, then that new RAM chip is defective.

 

[XxThatSamGuyxX]

Possibly... But before I waste time and money getting it returned, anything I might have overlooked?

 

[XxThatSamGuyxX]

Thank you Cave Man, I'll try that now.

 

[XxThatSamGuyxX]

So it's currently working with one new 2GB stick and an old 512MB stick... System profiler says it's running on 2.5GB and applications seem to be using a lot less virtual memory, but I don't understand why the new sticks won't boot together if they will with an older one...
Is leaving it with mismatched memory gonna cause any problems?

 

[Cave Man]

They are probably too high of frequency. The old chip forces the new chip down to the proper frequency (likely a tolerance issue), thus they work. Put both new ones in and their speed is incorrect and causing the problem. Macs are pretty picky, unfortunately.