iBook and a ram upgrade

Discussion in 'Mac Help/Tips' started by blogo, Dec 9, 2002.

  1. blogo macrumors 6502

    Apr 1, 2002
    Can i upgrade my iBook with 256mb pc133 ram, when the other 128mb ram runs on 100mhz?
  2. lmalave macrumors 68000


    Nov 8, 2002
    Chinatown NYC
    PC133 RAM is backward compatible in most cases, as far as I know. You should be fine.
  3. Bradcoe macrumors regular

    Apr 25, 2002
    Northeast U.S.

    YES. This is 100% ok. If the only difference between the PC100 and PC133 RAM is the clock speed which it runs at, then you are fine. This is because:

    PC133 ram is tested to run properly at 133MHz. PC100 is tested to run properly at 100MHz. What actually tells the ram what speed to run at is your system (be it FSB speed, memory controller, settings in the BIOS, etc). Running PC133 memory on a system that uses PC100 means that the ram will run at 100MHz. It can do this because 100MHz is slower than 133MHz and since it is tested to run at 133MHz, it will also be fine at anything less than this.

    On a side note, I have PC100 memory in a windows box of mine and the FSB is overclocked via the BIOS from 100MHz to 124MHz. The PC100 memory is running at 124MHz and even though its not rated at this, it is able to. I guess I got lucky and didn't get stuck with some ram chips that won't run as high. Now if I try to run it higher than 124MHz, the ram fails because this is too fast for it.

    This is probably way more than you wanted to know. =)

    When you buy ram for your iBook, just make sure it's the proper size. Just because its a PC100 (or PC133 in your case) SO-DIMM chip, doesn't mean it will fit. There are normal height SO-DIMMs and smaller height (Apples website says the size in inches) SO-DIMMs, which are what the iBook takes. I bought a 512 chip for my iBook when i first got it and thought it ordered a smaller SO-DIMM. Turned out to be the full size and there was NO way it was going to fit.

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