i have two ram chips: 128 onboard and an upgradeable 512mb (upped from 128 orig.) can i upgrade to 1 gb in the 512 slot? apple says no, but my computer guys put one in to test and it worked ok. they said apple may not have had 1gb chips avail at the time and later just didnt update the specs., but that there was a chance of a overheating issue. help, please.

Yes, you can use 1GB with no problems in this machine.

Actually there were two models that were an 867 MHz clock speed with different RAM capacities between the two. If you have the 15" Titanium PowerBook (characterized by a black keyboard) then the maximum RAM capacity for that machine was 1.0GB in two 512MB chips together. I suspect you have the next model though since you mention the 128MB chip on the logic board already. That model did only have one slot but you can place a 1GB chip in it just fine. I'm not sure why the discrepancy exists between what Apple says works in those computers and what actually happens but if you ever have any further questions on the subject search for a piece of software available for a free download called Mactracker. It lists nearly every device and even software created by Apple, most of the technical specifications for each item and history about it as well. I hope this helps!

Question, I just upgraded the ram in my powerbook g4. Now it sometimes boots up, sometimes doesn't. Sometimes it works ok, but iphoto and imovie won't start. Is it bad ram? I figure if it was then the system as a whole wouldn't boot ever. I also get this weird screen that locks the system up and says to reboot FF FF FF FF. Any ideas? I'm running a powerbook g4 1ghz machine, with (now) 1.25 ram. I'm not to familiar with macs, but I know on pc's with bad ram the computer won't boot