Mixing and matching RAM

Discussion in 'Mac Pro' started by mrbard, Apr 5, 2007.

  1. mrbard macrumors newbie

    Apr 5, 2007

    I was wondering whether or not it's possible to mix and match RAM on the Mac Pro's. I'd like to get 2 or 3 gigs of ram with the Mac Pro I'm ordering, but I saw the prices for ECC RAM was considerably cheaper at my local shop. So is it possible to get the 1GB option from Apple and then buy additional chips from my local shop?

    Are there any rules of thumb to remember in buying RAM? Do i need to have specific size ram chips or vendors or can they be mixed and matched at will?

    Thanks in advance for the help!

  2. CanadaRAM macrumors G5


    Oct 11, 2004
    On the Left Coast - Victoria BC Canada
    Yes, you can mix brands AS LONG AS the RAM you are ordering is 100% compatible with your Mac.

    Look for a seller who knows Macs, tests, and guarantees compatibility.
  3. brooker macrumors regular

    Apr 4, 2007
    rules of thumb:

    Here are the guidelines i'm going by in my RAM selection:

    • Everything has to be added in pairs of same-sized module. Pairs from different manufacturers will work fine (i.e. original 2x512 from apple + 2x512 from Crucial)
    • To maximize the 256 bit bus, you need 4 modules on the same riser (but the performance difference this makes is arguable).
    • Each chip has a controller that has work to do in storing and finding data -- using 8 x 512 chips will have a lot more overhead for these controllers (if you can use that much RAM) than 4 x 1GB, or 2 x 2Gb. More overhead means more heat.
    • Heat is the leading cause of CRC errors and shorter lifetimes -- So there really is something to getting a chip with a fanned heatsink rather than just a heat spreader.
    • Apple-certified really means that the chip deals with heat according to Apple's specs. Anything with a big heatsink would likely pass.

    So! my conclusion is to get 4 of the apple-certified 1GB modules from OWC. That should be plenty of ram for me for a while, and pretty much is the performance sweet spot. I'll still have plenty of room to upgrade, and I'll sell the stock chips to defray some costs. Want em?

    If your applications have unique RAM requirements, your configuration could need something different.

    Hope that helps!
  4. killmoms macrumors 68040


    Jun 23, 2003
    Washington, DC
    I got a couple WinTec modules that were listed as designed for the Mac Pro (came with big heatsinks and everything), but they conflicted with the Hynix modules that shipped with the MP—I was getting kernel panics randomly, even though memtest indicated everything was peachy over several tests. After some deliberation, I decided that returning the WinTec modules was too much hassle, especially since (absent the stock memory) they worked fine with no stability problems. I'll probably just buy two more WinTec modules to go up to 4GB (or 6GB, depending on my budget) to avoid headaches, and keep the originals around in case I ever need to send the box to Apple.
  5. mrbard thread starter macrumors newbie

    Apr 5, 2007
    excellent, that's exactly what i needed to know!

    Thanks for the help guys! :)

    Now i'm off to order my Mac Pro 2.66 quad ^-^
    Still can't believe I waited 5 months for an octo I can't even afford... :mad:

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