I brought home a Crucial PC2-6400 SO-DIMM 4GB kit from Microcenter today. I popped out my pair of 1GB sticks of PC2-5300 from my 2007 2.4 GHz Aluminum iMac, popped in the new RAM, and turned it on. I heard the fan and drive spin up, but that was it. The screen stayed black and the boot chime never sounded. In fact, the machine made no sound from the speakers at all.
I went through a few iterations of one DIMM at a time in either slot, and found that as long as only PC2-6400 RAM was installed, the machine wouldn't boot. I thought DDR2 RAM speeds were backwards compatible and that my 800MHz RAM would run fine at the 667MHz speed of the iMac. Am I completely mistaken? It seems weird that both sticks of RAM would be bad...
I haven't had a chance to boot with one of my 1GB sticks of 667MHz RAM and one of my 2GB sticks installed simultaneously (I'm currently duping over my hard drive from an external enclosure because I upgraded to a 2TB drive today). As soon as that's done, I'll run some memory tests (if I can get the machine to boot completely in the mixed RAM configuration, that is - I only confirmed a boot chime and haven't tried booting to the destkop yet) and find out for sure if either DIMM is bad.
Do you folks have any thoughts?