48 GB RAM 1333 MHz in flashed Mac Pro 5,1 working as 1066 MHz

Discussion in 'Mac Pro' started by Spacedust, Oct 5, 2012.

  1. Spacedust, Oct 5, 2012
    Last edited: Oct 5, 2012

    Spacedust macrumors 6502a

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    #1
    I just replaced 6 stock Apple Hynix modules 2 GB (12 GB RAM) 2Rx8 with 6 Micron DDR3 PC-10600 2Rx4 (48 GB RAM) and all is working but their being shown as 1066 MHz.

    This is a Mac Pro 4,1 flashed to 5,1 on Mountain Lion 10.8.2 + supplementary fix.

    What I need to do to have 1333 MHz speed ?

    I've heard it might work with Nehalem CPU's or do I need Westmere ?

    http://arstechnica.com/apple/2011/0...nsform-a-2009-mac-pro-into-a-12-core-monster/

    "Even if you didn't plan to upgrade the CPU, though, there are other benefits. Some Nehalem CPUs can support 1333MHz DRAM speeds, but are limited to 1066MHz on the older Mac Pros. The firmware update will enable the full 1333MHz speed if you have a CPU and RAM combo that can support it."
     
  2. 666sheep macrumors 68040

    666sheep

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  3. beto2k7 macrumors 6502

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    #3
    I'm assuming you have the X5570 on that pro... according to intel it supports 1333mhz ram.
     
  4. Umbongo macrumors 601

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    #4
    Right, but Spacedust has Xeons that support 1333MHz memory.
     
  5. 666sheep macrumors 68040

    666sheep

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    #5
    2.93 Nehalem is one of "some" AFAIK.

    If it's only System Profiler read fault, PRAM reset will help. If problem is HW based, it obviously won't. Recently I've flashed reference 4870 and after flash ASP and Expansion Slot Utility was telling that it runs @PCIe x8 and it's maximum supported speed. PRAM reset brought things to normal (PCIe x16).

    @beto2k7: you cleverly edited your post, but Umbongo is blazing fast ;) :p
     
  6. Loa macrumors 65816

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    #6
    Hello,

    You know that the time you lose on this issue will never be regained by an increase in RAM performance? :p

    Loa
     
  7. Spacedust thread starter macrumors 6502a

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    #7
    Yes. I got dual X5570 - genuine Apple CPU's :)

    I will try resetting PRAM.

    ----------

    Not working :/ I still got 1066 MHz reported.
     
  8. Umbongo macrumors 601

    Umbongo

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    #8
    What is the part number of the memory you have?

    The only way to get 1333MHz speeds with Nehalem CPUs is with no more than one 1.5v single-rank or dual-rank DIMM per memory channel.

    So while it doesn't seem to be the issue, using quad-ranked DIMMs or having more than 2 on any channel or using 1.35V DIMMs would not allow speeds of 1333MHz.
     
  9. loybond macrumors regular

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    #9
    Umm... there's no such thing as a "genuine Apple CPU."

     
  10. Spacedust thread starter macrumors 6502a

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    #10
    I know. The one without heatspreaders ;)

    ----------

    I use such modules:

    [​IMG]
     
  11. Umbongo macrumors 601

    Umbongo

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    #11
    Well nothing about that memory should be causing it to run at 1066MHz so that shouldn't be the issue.
     
  12. 666sheep macrumors 68040

    666sheep

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    #12
    Some people on Apple discussions forum reported that same issue with real 5,1 MP with 3.2 Nehalem using 1333 memory.

    This could be an answer. OP, read this: https://deinoscloud.wordpress.com/2...intel-nehalem-memory-architecture-connection/ and try different slot population options.

    ...or leave it like that because (as Loa said) performance difference is minimal, at least according to Geekbench.
     
  13. Spacedust, Oct 6, 2012
    Last edited: Oct 6, 2012

    Spacedust thread starter macrumors 6502a

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    #13
    I will try all combinations also removing some sticks and we will see if this would help ;)

    That was preety scary at first because instead of 48 GB RAM system profiler showed me 32 GB and red LED's popped out. Reseating all RAM modules fixed this problem.
     
  14. Spacedust thread starter macrumors 6502a

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    #14
    I've tried different configurations and it always work on 1066 MHz.
     
  15. 666sheep, Oct 7, 2012
    Last edited: Oct 9, 2012

    666sheep macrumors 68040

    666sheep

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    #15
    So one thing left: quad rank vs dual rank. As Umbongo said before, it must be this. In article I've inked in my previous post you can find below table:

    [​IMG]

    Your RAM is quad rank, so according to table it won't work @1333 with Nehalem CPUs, if I understand this correctly.

    Table might be useful for someone at least.
     
  16. Umbongo macrumors 601

    Umbongo

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    #16
    I looked at the memory he has and it is listed as dual-ranked on all sources. I think there are some "why is my memory running at 1066MHz posts on this forum that have had similar issues with 2010 Mac Pros, might be worth looking at if it bothers you Spacedust.
     
  17. Spacedust thread starter macrumors 6502a

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    #17
    My memory is 2Rx4 so Dual Ranked ;)

    If anyone got Nehalem working with 1333 please let me know.
     
  18. avemestr macrumors regular

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    #18
  19. 666sheep macrumors 68040

    666sheep

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    #19
    Stupid me :eek: it is 2Rx4

    Edited my previous post.
     
  20. Spacedust thread starter macrumors 6502a

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    #20
  21. macmesser macrumors 6502a

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    #21
    In this computer which slots correspond to which channels? I have the same one, also flashed to 5,1. I have 4X8GB 1333 DDR3 ECC RAM kit from OWC. How would I populate the slots to get 1333MHz speed? How do I tell if the DIMMS are single, dual or quad ranked and what does that mean? Thanks for any insights.
     
  22. BlueWaterVA, Oct 11, 2012
    Last edited: Oct 11, 2012

    BlueWaterVA macrumors member

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    #22
    1333 Ram

    FYI:
    I am running 24 GB of Kingston MP1333DRK3 mem with a W3680 and my readout is 1333Mhz. No problem. (see attachment)

    As a side note: since the X58 chipset used by the Mac Pro uses a triple channel memory controller in the CPU, it may be getting confused with all 4 mem slots populated. The mem needs to be in slots 1,2 & 3. Slot 4 is a lost cause as far as I know.
     

    Attached Files:

  23. macmesser macrumors 6502a

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    #23
    I thought slot 4 knocked out triple channel advantage, which has to do with efficiency of memory access, but doesn't have any effect on RAM speed. If that's so then putting in a slower DIMM would set the pace for all the other DIMMs but as long as all the modules are the same speed that's the speed you get. So with 4 slots populated you get the nominal RAM speed but it's accessed a little less efficiently. I seem to recall comments by some knowledgeable posters that generally the extra RAM is more advantageous than the slightly greater efficiency of the triple channel access.
     
  24. Umbongo, Oct 12, 2012
    Last edited: Oct 12, 2012

    Umbongo macrumors 601

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    #24
    The Nehalem memory controllers supported 1333MHz memory speeds only when there was 1 DIMM per channel. Plenty of boards allowed this to be overridden which is why it was never of note in the consumer space. You could easily get 6 DIMMs working at 1333MHz on a Core i7 920 which didn't support that speed at stock specifications. ASUS even had their dual processor boards allow it to be overwritten. Apple of course don't do such things and that is probably the reason they limited memory speeds to 1066MHz despite half the processors supporting faster speeds.

    When Westmere came out the memory controller was changed so that when using 2 DIMMs per channel you could still get 1333MHz speeds.
     
  25. macmesser, Oct 12, 2012
    Last edited: Oct 12, 2012

    macmesser macrumors 6502a

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    #25
    Interesting. About the memory controller change with Westmere, would that have been done in firmware or was it a different chip?

    BTW, what channel are DIMMs in MP slot 4 or 8 on? Do they share a channel with another slot?
     

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