After installing Appleis FirmWare Updates on various computers (FireWire PowerBooks and PowerMac G4s) here at The Mac Observer Labs, we instantly realized there were problems with the computers recognizing their full compliments of RAM. While the details are still fuzzy, there is definitely a link to non-Apple RAM. In one PowerBook, we had a 256MB chip in the bottom slot, with no chip in the top slot. After the firmware update, the machine wouldnit boot. Instead it gave us one long beep and froze. According to the FireWire PowerBook service manual, this beep indicates no RAM. We found a 64MB chip, plugged it in and it worked.

On another PowerBook, we had two non-Apple chips installed. The bottom slot contained a 256MB chip and the top slot had a 128. Upon reboot after the Firmware update, the machine reported only 256MB RAM, and the Apple System Profiler indicated no 128MB chip in the top slot. We removed the 128MB chip and replaced it with the original 64MB chip that came with the machine, and it recognized that fine. So while SOME non-Apple RAM will work, it is clear that not all of it will work. Thus far, here is what we have found:

256MB PC100-222S non-Apple chip - Works fine.
256MB PC100-222S non-Apple chip - DOES NOT WORK
128MB PC100-222S non-Apple chip - DOES NOT WORK
64MB PC66-333 non-Apple chip - Works fine.
64MB PC100-222S Apple-installed chip - Works fine.

As you can see, there is no rhyme or reason to the types of chips here, although it seems as though all Apple factory-installed RAM definitely DOES work after the update. We contacted Apple support and they indicated that it was up to the third party RAM vendors to fix this problem.