New Mac Pros: DDR2-667 vs. DDR2-800 RAM

Discussion in 'Mac Pro' started by smirkingboy, Feb 10, 2008.

  1. macrumors member

    Apr 5, 2007
    Does anyone know what the performance difference, if any, would be between these two RAM specs?

    The Apple Store, I have read, is currently installing DDR2-667 in the new Mac Pros, even though it will take DDR2-800.

    Most third party RAM vendors are offering 667. Crucial has only the 1GB sticks of DDR2-800. Ramjet, on the other hand, has all sizes of DDR2-800: 16GB (8x2GB) is about $1100.

    Additionally (for bonus points kids):

    Heres where I comically reveal how I know nothing about computers, but please bear with me. The frontside bus of each processor is a dual 1600 MHz. Does that mean that each processor can "send" 3200 MHz to the RAM ? That would provide a total of 6400 MHz, to 8 bays of RAM, which is 800 per, so is that why the new RAM specs are 800 ?
  2. macrumors regular

    Jan 8, 2008
    barefeats has tested the new mac pro with 667MHz ram, and it works... A tiny bit slowly in memory benchmarks of course, but the difference seems to be minimal in everyday use (and quite disappointing I think in regards to 800MHz added performance...)

    So if you really need a lot of memory, then going 667MHz could be a good choice. I am not sure about the mixing of speeds, but I would suppose the 800MHz would align to the slower ones... (Where did you read that apple put 667MHz memory btw ?)

    As for details about the ram in mac pro, go to read anandtech website, which has very good information (for the first mac pro, but still accurate I think)

  3. macrumors 6502a


    Jul 21, 2007
  4. macrumors 68000


    Jul 1, 2004
    I've got 16gb of 667mhz RAM running in the new 2.8 octo MP. Runs great.
  5. macrumors G5


    Oct 11, 2004
    On the Left Coast - Victoria BC Canada
    Don't put 667 MHz FB-DIMMs into the Penryn machines, it will be unstable (and obviously, slower than it should be). They are designed for 800 MHz RAM, and the older MacPros are designed for 667. Don't attempt to mix and match.
  6. macrumors regular

    Feb 8, 2008
    I bought 8GB in 2GB sticks @ 800MHz. I'll probably buy another 8GB next month. Bearfeats guy said the Mac Pro performed better when fully loaded with 2GB sticks of RAM.
  7. macrumors 6502

    Jan 30, 2008

    am I missing something here?
    my mac pro came with (2 x 1gb) DDR2-800 sticks...and I added 2 more 800 in there....

    they dont come with 667, they come with 800...or at least mine did...
  8. macrumors 68040

    Dec 13, 2004
    The reason why a lot of people use 667 over 800 is that it's cheaper and the performance is very close all other hardware equal.

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