12 core 2.66mhz only showing 1066 for ram speed! What's up??

Discussion in 'Mac Pro' started by djtorch, Nov 7, 2011.

  1. djtorch macrumors newbie

    Joined:
    Nov 7, 2011
    #1
    I have recently purchased a 12 core 2.66 Mac Pro. The specs read that my machine will do 1333mhz. It originally had 1066 ram loaded in it (don't ask me why), but I recently loaded it with 1600 memory, thinking I'm going to get 1333. At first I really thought I saw this speed come up in the "about this mac". But, today it only reads 1066. Is there something I need to do to get this up to 1333?

    Help!
     
  2. johnhw macrumors 6502

    Joined:
    Jun 16, 2009
    #2
    If it is mixed with 1066 RAM, every RAM will work at 1066MHz.
     
  3. Loa macrumors 65816

    Loa

    Joined:
    May 5, 2003
    Location:
    Québec
    #3
    Hello,

    Can you do real world tests that show a difference in performance between 1066 and 1333?

    Loa
     
  4. fairbanx macrumors member

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    Feb 18, 2010
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    Germany
  5. Umbongo macrumors 601

    Umbongo

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    Sep 14, 2006
    Location:
    England
    #5
    You've not given near enough information. You need to tell us the manufacturer and model of all the memory sticks used, how many and where they are placed.

    The specification is that you will only get 1333MHz speeds running dual-rank ECC Unbuffered 1333MHz DIMMs - where you are running 1600MHz non-ECC unbuffered.
     
  6. beto2k7 macrumors 6502

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    ::1
    #6
    If there wasn't any difference then 1333 ram wouldn't exist. For cientific applications there is a noticeable performance increase. For some of us that's real world.
     
  7. Inconsequential macrumors 68000

    Joined:
    Sep 12, 2007
    #7
    True, but tends to be small for anything but the most memory demanding applications!

    On a side note, i'm currently over clocking my Mac Pro's 2009 DDR3 533Mhz sticks 2GB sticks, to see what they manage (In a AMD board - not in the MP!)
     
  8. Mac_Max macrumors 6502

    Joined:
    Mar 8, 2004
    #8
    Most 1066 DIMMs will have tighter timings than 1333 speed DIMMs so the difference will likely be less than the clock speed would seem to dictate.
     
  9. djtorch thread starter macrumors newbie

    Joined:
    Nov 7, 2011
    #9
    My Mac is "still trippin'"

    This is what I did. I took out the 1600 mhz stuff because it was not ECC. I paid 3 times that amount to get some ECC "server" ram. The brand is Super Talent and the model name is STT DDR3-1333 MHz 8GB PC3-10600 ECC REG Hynix Chip Server. The Mac Pro's chip configuration told me that everything was cool (in the right slots). But, still no 1333!!! only 1066. I contacted Super talent to see "what's up" but maybe someone here can tell me what's going on? I would like to get some sleep tonight :-[!
     
  10. fairbanx macrumors member

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    Feb 18, 2010
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    Germany
    #10
    Did you try PRAM Reset with these newer ones?
     
  11. Gonk42 macrumors 6502

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    Jan 16, 2008
    Location:
    near Cambridge
    #11
    The 5500 series Xeon chips would switch the RAM down to 1066 from 1333 if there was more than one on any of the three channels (i.e. if all 4 ram slots on the Mac Pro were occupied for either of the processors).

    I thought that the 5600 series in the 12 core Mac Pro allowed 1333 operation regardless, but if you have all slots used it might be worth experimenting with just 3 per processor.
     
  12. Umbongo macrumors 601

    Umbongo

    Joined:
    Sep 14, 2006
    Location:
    England
    #12
    Still not giving enough information to us. How many DIMMs are you using?

    Gonk42 is correct in that using more than one DIMM per channel (i.e 4 per CPU with Mac Pros) takes the speed down. This was corrected with Westmere so that you could use two unbuffered ECC DIMMs per channel and get 1333MHz still.

    So if you want 1333MHz speeds you need to use only 1 DIMM per channel - 3 per CPU; or use unbuffered ECC 1333MHz DIMMs. Honestly the speed difference isn't something you should worry about.
     
  13. ljonesj macrumors 6502a

    ljonesj

    Joined:
    Oct 20, 2009
    Location:
    Kingsport TN
    #13
    if you are mixing the 1066 mhz chips with the 1333mhz chips you will only run at 1066
     
  14. maxmaut macrumors regular

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    Nov 13, 2011
    #14
  15. Incubus27 macrumors newbie

    Joined:
    Dec 29, 2011
    #15
    The RAM speed is completely dependent of the CPU RAM/Memory controller, hence a Westmere machine with X56XX CPUs will run its RAM at stock speed (1333 Mhz) given that the RAM installed is that spec. Xeons with the letters W run in Single/QPI; Xeons with the letter E have low power TDP but have 2 QPI lines which indicate they can share a dual MAC Pro setting. However the RAM needs to be 1333 Mhz to run at that speed. Westmere Xeons use triple channel too, the recommended setting is 6 ram sticks to have the CPU memory controller to run in triple channel mode, having all RAM populated causes the CPU Memory Controller to run in dual channel. There's a nifty firmware hack that allows the Mac Pro 4,1 to run Westmeres CPUs. Once the internal firmware has been updated, the logic board will be able to use Westmere CPUs.
     

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