RAM questions

Discussion in 'Mac Basics and Help' started by DarkSilver2, Jul 9, 2005.

  1. DarkSilver2 macrumors member

    Jun 22, 2004
    I have a few questions for minds greater than my own. I want to increase the amount of RAM in my iMac G4 (1.25 GHz, 167 MHz bus) by 1 GB, but I don't know if it is possible. My questions are these:
    1) Can a G4 iMac handle a 1 GB stick of RAM?
    2) Can a computer with a 167 MHz bus use 333 MHz RAM at a slower speed?
    3) Is there a limit to the amount of RAM an iMac can use (ie is there a point over which more RAM will have no effect)?

  2. DarkSilver2 thread starter macrumors member

    Jun 22, 2004
    Well, I just saw on Crucial.com's website that my computer will only support 1024 MB of RAM. My question therefore changes to how one would determine this information by theirself.
  3. CanadaRAM macrumors G5


    Oct 11, 2004
    On the Left Coast - Victoria BC Canada
    1) The iMac G4 DDR models (1 GHz and up) can take up to 2 Gb of RAM, with a 1 Gb SODIMM in the user-accessible socket, and 1 Gb (theoretically) in the internal technician-accessible DIMM socket.

    2) The iMac G4 1.25 GHz REQUIRES 333 MHz memory - otherwise known as PC2700. PC2100 (266 MHz) RAM will not work. The memory buss is 167 MHz -- DDR stands for Double Data Rate - it performs a memory option on both the leading and trailing edge of the buss clock - so 167 MHz x 2 = 333 MHz effective speed.

    3) Every computer has a limit above which the memory controller cannot address the rows and columns of memory on the chip. The iMac G4 (DDR) machines were initially specified by Apple at 1 Gb maximum because 1 Gb modules were not common at that time, however the memory controller could read 2 Gb just fine. Apple (and Crucial) have not updated their specifications. However this is an isolated case. 95% of the time, the manufacturer's stated spec is the actual limit of the memory controller. Your basic assumption should be that the Apple spec is correct.

    The iMac G4 <1 GHz with PC133 SDRAM is limited to 1 Gb RAM with 2 x 512 Mb. There are no 1 Gb PC133 SODIMMs or non-registered, non-ECC 1 Gb PC133 DIMMs that will work in the machine.

    Unless you can decipher the technical specifications of the memory controller chip, you have to rely on a RAM vendor who has actually tested the modules and guarantees them for your specific model of Mac.


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