64GB Ram in 4 & 6 core 2009-2012 Mac Pro's...

Discussion in 'Mac Pro' started by funwithdesign, Jan 29, 2014.

  1. funwithdesign macrumors regular

    Joined:
    Dec 9, 2011
    #1
    There has been a fair bit of discussion about this over the years and it appeared that the max ram for single processor models was 48GB (3x16) but these guys are selling a 64GB kit for single processor models.

    http://macramdirect.com/macpro.html#mp4

    Anyone have experience with this or willing to order?
     
  2. echoout macrumors 6502a

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    Aug 15, 2007
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    Austin, Texas
    #2
    I'm not seeing any "3x" kits on that page that go above 48GB. You don't want to use the 4th slot.
     
  3. weaverra macrumors regular

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    Sep 27, 2006
    #3
    And why not? It's there for a reason. This is Apple we are talking about. If it wasn't needed they wouldn't have put it on there.
     
  4. funwithdesign thread starter macrumors regular

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    Dec 9, 2011
    #4
    Who said anything about 3x kits? The 64GB is a 4x16 kit.

    The 3 slots vs 4 slots is a performance issue and a slight one at that. The previous issue was that nobody sold 16GB modules that worked up to 64GB in the single cpu systems. It's not an OS limit obviously as the dual models can take 128GB.

    These guys appear to sell modules that they say work up to 64GB. I'm just wondering if anyone has tried.
     
  5. Draeconis macrumors 6502a

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    May 6, 2008
    #5
    The 2009 - 2012 models are tri-channel with 4 slots, with 1 and 4 sharing bandwidth to the CPU.

    The slot nearest to you as you remove the CPU daughterboard is slot 4.

    The bandwidth limitation of sharing slots 1 and 4 isn't too bad, definitely not as good as having a dedicated channel for each memory slot, but hey.

    Maximum the single CPU models can take is 64Gb, max for dual CPU models is 128Gb, although apparently Mountain Lion had a limit of only being able to address 96Gb. As far as I know, Mavericks addresses this, and can address all 128Gb.
     
  6. echoout macrumors 6502a

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    #6
    Sorry I misunderstood. I'm confused why you posted this. 16GB sticks that work fine (at 1066) have been available for a long time.
     
  7. echoout macrumors 6502a

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    #7
    It knocks the speed of your RAM down from 1333Mhz to 1066Mhz to use the 4th and 8th slots. That can be significant, depending on what you're doing.
     
  8. funwithdesign thread starter macrumors regular

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    Dec 9, 2011
    #8
    That's not the issue. I know 16GB modules work, but nobody has sold a kit for the single cpu models that include four 16GB modules.

    OWC could not get it to work when they originally tried a while ago.

    That's not quite accurate. It doesn't drop the speed down to 1066, Slot 4 will run about 5% slower due it being shared. The benefit of more ram will be greater than such a small difference.
     
  9. echoout macrumors 6502a

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    #9
    What's the difference between a kit and 4 identical sticks? Not being a smartass, I just don't follow. (never mind, I see the note on OWC now. Weird.)

    And on the 5% loss, I'm clearly confused on that too. When I load up all 8 slots, the other first six show as 1066. When I load the 6, they show as 1333.

    Help me out here!
     
  10. tobyg macrumors 6502a

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    Aug 31, 2004
    #10
    I have a Mac Pro 4,1 with 3 16GB DIMM's. I actually have 4, but the machine doesn't boot with the 4th in. To be more accurate, it does appear to boot but has no video. My guess is the chipset doesn't remap the video card rom properly, or if it does remap it, the system isn't able to address it. The system chimes and tries to boot but all I get is a white screen. I have not tried connecting to it over the network with ARD or VNC to see if it's actually running.
     
  11. funwithdesign thread starter macrumors regular

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    Dec 9, 2011
    #11
    Good to know.

    I know that the original 16GB modules being sold were quad ranked and that was the issue. I'm just wondering if these modules on this link are dual ranked or some other difference and they work.
     
  12. tobyg macrumors 6502a

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    Aug 31, 2004
    #12
    My modules are dual ranked, 16GB 2Rx4 PC3-12800R. Even quads should work. Actually I'm not sure about the W3500/W3600 series Xeon's, but the 5500/5600 Xeons can address 24 ranks per CPU.

    I don't think it's a rank issue, I think perhaps the W3500/W3600 chip or the chipset can only address 48GB. It would be interesting if someone with a single 5500/5600 series chip in a single processor system could try 64GB and see if that works. Supposedly 128GB does work on the dual processor systems (obviously with 5500/5600 chips).
     
  13. weaverra macrumors regular

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    Sep 27, 2006
    #13
    Sounds as if you have other problems possibly with the memory.
     
  14. tobyg macrumors 6502a

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    Aug 31, 2004
    #14
    What? I have no problems with my memory. It's rock solid. It's been tested by others, 4 16GB DIMM's do not work in single processor systems. That's the whole point of this thread, the OP found someone selling 4x16 and is questioning if it's now working. I believe it's not and the seller selling 4x16 is unaware it doesn't work.
     
  15. xcodeSyn macrumors 6502a

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    Nov 25, 2012
    #15
    Perhaps you need to read this link before making incorrect statements and it is further confirmed by tobyg in the previous post.
     
  16. funwithdesign thread starter macrumors regular

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    Dec 9, 2011
    #16
    Yes exactly. My thoughts at first were that they just didn't know, but they do mention the aspect of not being able to mix 16GB modules with other sizes which then leads me to believe they somewhat know what they are talking about.

    Just don't know.
     
  17. h9826790, May 8, 2014
    Last edited: May 8, 2014

    h9826790 macrumors 604

    h9826790

    Joined:
    Apr 3, 2014
    Location:
    Hong Kong
    #17
    Yes, it's confirmed same thing happen on my 2009 Mac Pro [Flashed 5,1].

    When I load up all 4 slots with 32G of RAM, the max speed is only 1066MHz (SMC and PRAM reset won't help).

    But Once I remove the RAM from the 4th slot, the remaining 24G of RAM can run at 1333MHz.

    And that 5% is overall performance.

    4x8G RAM vs 3x8G RAM
    Geekbench average.png Screen Shot 2014-05-09 at 14.28.43.png

    If only consider the score from RAM itself. The score jump from about 1600 to 2400. It's a 50% improvement!
     

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