Many PowerBook G4 users are experiencing failures of the lower memory slot. I have found a workaround for the problem, though not quite a full solution (as it won't survive a reboot). Note that very little testing has been done on this fix, but I have used it on my PowerBook with 100% success. First, I confirmed my lower slot is not fried by starting up with a single DIMM in the lower slot, which worked. However, the Mac still will not recognize the lower DIMM if there is memory in both the upper and lower slots. This may be different to what others are experiencing so your mileage may vary. [robg adds: Note that this hint involves the use of Open Firmware, and you could permanently damage your machine by following this procedure. Proceed at your own risk, as macosxhints.com will not be held liable fo...

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