Old Mac Pro 667mhz memory in New 800mhz Mac Pro - mix and match ok?

Discussion in 'Mac Pro' started by pprior, Feb 3, 2009.

  1. pprior macrumors 65816

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    #1
    Can you mix old mac pro memory in the new mac pro?
     
  2. pastrychef macrumors 601

    pastrychef

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    #2
    It will work, but it will cause all the memory to run at 667MHz and, hence, you will take a bit of a performance hit.
     
  3. hatehereyes macrumors 6502a

    hatehereyes

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    #3
    I might be wrong but i thought the old mac pro memory wasn't FB-DIMM but just regular ddr2 memory?
    If that's the case i don't think it would even fit in the 2008 mac pro DIMM slot.
     
  4. sidewinder macrumors 68020

    sidewinder

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  5. Tallest Skil macrumors P6

    Tallest Skil

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    #5
    Wrong. They're both FB-DIMMs. The first was 667 and the current is 800.

    But the next Mac Pro won't be FB-DIMMs and will run at 1333.
     
  6. tom. macrumors 6502

    tom.

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    #6
    I think it will run but it is not advised. The price difference isn't substantial enough.
     
  7. pprior thread starter macrumors 65816

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    #7
    Thanks, all.

    Apple is replacing my old mac pro with new one and I have 11gb of old ram and new one coming with 8gb, wondering if I could fill remaining 4 slots without having to buy new memory.
     
  8. TrapOx macrumors 6502

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    #8
    Another unsubstantiated guess.
     
  9. pastrychef macrumors 601

    pastrychef

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    #9
    As I've said before 667MHz FB-DIMMs will work fine in the 2nd gen Mac Pros but will cause all the RAM in the machine to run at 667MHz instead of the optimal 800MHz.

    I know it works because I did that when I first transitioned from 1st gen Mac Pro to 2nd gen.
     
  10. pprior thread starter macrumors 65816

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    Aug 1, 2007
    #10
    Thanks - that's exactly what I wanted to hear. 1st hand experience always trumps the internet experts who repeat what they've read somewhere.

    The barefeats reference was also very helpful - I'm actually quite shocked how little an impact it seems to cause - from 0 to 4% hit.
     

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