Can I put DDR3 ram in my pro?

Discussion in 'Mac Pro' started by Macpropro80, Feb 15, 2009.

  1. Macpropro80 macrumors 6502

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    Jan 31, 2009
    #1
    Another Noob question (sorry)

    Can I put DDR3 Ram in my mac pro? the Bus Speed is fast enough. If the Slots cant take DDR3 is there any 3rd party memory racks (the 2 cards that hold the ram) that I can put in my mac pro to support DDR3?
     
  2. r.j.s Moderator emeritus

    r.j.s

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  3. Intel Inside macrumors 6502

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  4. TrapOx macrumors 6502

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  5. Macpropro80 thread starter macrumors 6502

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    #7
    Is there any 3rd party Riser card (I forget the real name, the 2 cards you put ram on in the pro) That supports DDR3 Ram?
     
  6. TrapOx macrumors 6502

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    #8
    Not unless you buy a 3rd party motherboard along with it.
     
  7. peskaa macrumors 68020

    peskaa

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    #9
    No.


    Your Mac Pro will take DDR2 FB-DIMMs only. End of story.
     
  8. bozz2006 macrumors 68030

    bozz2006

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    #10
    no. DDR2 and DDR3 are completely different. they are not interchangeable in any way.
     
  9. Sun Baked macrumors G5

    Sun Baked

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    May 19, 2002
    #11
    Yep, it is called selling your Mac Pro and buying a new one that supports DDR3.

    Edit: something that may likely happen with the next Xeon dual CPU chipset.
     
  10. Anonymous Freak macrumors 601

    Anonymous Freak

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    #12
    Nope.

    The current (and all previous) Mac Pros use "DDR-2 FB-DIMMs". They aren't even "normal" DDR-2" They are a special variant of DDR-2 that has an onboard chip (called "AMB", the "Advanced Memory Buffer") that turns the normally parallel memory protocol into a much faster (clock-speed-wise,) serial connection. This means that many fewer pins are necessary for data; which means you can have many more memory channels. (Back when FB-DIMMs were new, two channels was about all any system had; FB-DIMMs made four channels easily possible.)

    THEORETICALLY, it would be possible to make a new AMB chip that allows faster DDR-3 chips to reside on the module, yet it would connect to the exact same FB-DIMM connector.

    The problem is that the connection from the memory controller to the AMB on the current Mac Pro is only fast enough for DDR2-800. So even if you threw DDR3-2133 on those modules, the memory controller wouldn't know what to do with the extra speed. (And, to my understanding, nobody makes DDR-3 FB-DIMMs yet, anyway.)

    So it's a chicken-and-egg scenario. No FB-DIMM systems run faster than 800 MHz (equivalent,) so nobody makes FB-DIMMs faster than 800 MHz.


    Edit to summarize: Nobody makes a replacement riser card; but such a card wouldn't even be necessary, since by its design, FB-DIMMs only need a new on-DIMM AMB to support a new memory technology such as DDR-3. But even if they *DID*, it wouldn't matter to the Mac Pro because its memory controller wouldn't support the faster speed.

    It's like trying to run 94 octane gas in a Honda Civic. The engine can use it, it just can't take advantage of the higher octane properly. (In fact, using higher octane gas than your car needs actually *REDUCES* power and fuel efficiency.)
     
  11. Tallest Skil macrumors P6

    Tallest Skil

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    #13
    Change "may likely" to "will" and/or "have to". :)
     
  12. TrapOx macrumors 6502

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    #14
    More guesses. Unless you're a developer, you're absolutely clueless.
     

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