I just put 2 sticks of 512mb in my g5 with these specs pc3200r-30330, the machine doesn't recognize them. I notice that the existing ram got this on the label pc3200u-30330. Pease someone tell me the difference between these 2.
R = Registered or Buffered (usually seen only in Error Correcting (ECC) RAM
U = Unbuffered or standard RAM (Could be ECC or non-ECC, although Non-ECC is standard for almost all desktop and consumer machines)
Count the number of RAM chips on the module. If it is a multiple of 8, then it is non-ECC.
But if it is a multiple of 9, then it is ECC RAM and not appropriate for your Mac. If it says Reg. or Buffered anywhere on the label, it is also not for the Mac.