I'm in the process of upgrading the innards of an early 2008 15" MacBook Pro (4,1). I bought a couple of 2GB sticks from OWC, but have run into trouble with the new RAM. The laptop refuses to boot with both 2GB sticks installed -- the power light comes on, the optical drive revs up, but no startup chime and I get a black screen. If I insert one 2GB stick and one of the original 1GB sticks, it boots up as normal and reports 3GB total. It doesn't seem to make any difference which RAM sticks I install or which slots I insert them into.

Does this model just not work with 4GB RAM for some reason? I haven't run across any mention of quirks regarding memory upgrades with the usual suspects (LowEndMac, EveryMac), so I assumed this wouldn't be a problem.

EveryMac shows it should do 6GB... Have you zapped PRAM (CMD-Option-P-R) for 3 chimes before booting? Have you reset SMC?

Looks like this was discussed in a number of Apple community threads and the understood culprit was faster ram labeled & sold as slower ram. Manufacturers were phasing out the 667mhz ddr2 & started using 800mhz in its place. Per the Apple thread, that is why the faster stick works in tandem with the slower one. The Mac knows to clock down to the slower 667 speed but has a hard time what to do with the 800mhz sticks only. Here's the thread I am speaking to.

Here

I had no idea. I've not run into this before on my own.

>> phunguss said:

Have you zapped PRAM (CMD-Option-P-R) for 3 chimes before booting? Have you reset SMC? Click to expand...

Yep, did both, and that had no effect on the laptop booting.

>> Certificate of Excellence said:

Looks like this was discussed in a number of Apple community threads and the understood culprit was faster ram labeled & sold as slower ram. Manufacturers were phasing out the 667mhz ddr2 & started using 800mhz in its place. Per the Apple thread, that is why the faster stick works in tandem with the slower one. The Mac knows to clock down to the slower 667 speed but has a hard time what to do with the 800mhz sticks only. Here's the thread I am speaking to. Here Click to expand...

Ah, thanks for that link. I didn't suspect it was a RAM frequency issue given that System Profile reports both of the 2GB sticks running at 667mhz. Still, that discussion thread matches exactly with my experience. I guess I'll be living with 3GB instead of 4 with this particular machine -- good thing the RAM kit was only $15 ¯\_([katakana-letter-tu])_/¯.