I ran into the most interesting puzzle ever with my Mac today. I run a G4 450Mhz AGP etc.. It came with stock of 128 MB of RAM PC-100. The 128MB chip is in the first slot. Then I added a 256MB PC-133 in the second slot a year ago. Sofar everything worked great and the Mac read the correct total of RAM. Today I installed a 512MB PC-133 of RAM in the 3rd slot. Booted up the Mac and went to "About this Mac", and the Mac only read the 2nd and 3rd slots of RAM. It didn't recognize the 1st slot of 128MB. I thought that was strange. So then I got to thinking well maybe the Mac wants to read from high to low in memory? So I put the 512, 256 and 128 in that order. (1st, 2nd, 3rd, slot) Booted up the Mac again, still only read the 512 and 256 of RAM. So then I decided to put the 512 in the 2nd slot, 256 in the 3rd slot and the 128 in the 4th slot and leave the 1st slot open. FINALLY my Mac recognized all three pieces of RAM. Now hopefully because it recognizes it, that it ACTUALLY is using all three sticks.
Anyone know why the Mac didn't recognize the 128MB in the 1st slot after putting the 512 in the 3rd slot to begin with?