'09 Mac Pro Quad 2.6 Ram... 6 gigs? 8?

Discussion in 'Mac Pro' started by whyrichard, Sep 1, 2009.

  1. whyrichard macrumors 68000

    Joined:
    Aug 15, 2002
    #1
    Hey,

    It seems upgrading the Ram on the '09 Mac Pro is a little wierd. So 6 gigs is what is recommended? doesn't that leave one slot open? Shouldn't things be paired in threes on this machine or something like that?

    Whats the word on the ram on this machine?

    thanks,
    r.
     
  2. Umbongo macrumors 601

    Umbongo

    Joined:
    Sep 14, 2006
    Location:
    England
    #2
    Simply put: having a fourth DIMM reduces the speed of the memory due to the way the memory controller works.

    Realistically even with 4 DIMMs it is faster than anything there was before and if you are utilizing more than 6GB (which with OS X you probably are/can) then having more slower memory is better than having to page out to a hard disk.
     
  3. kornyboy macrumors 68000

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    Knoxville, TN (USA)
    #3
    Wirelessly posted (iPhone: Mozilla/5.0 (iPhone; U; CPU iPhone OS 3_0_1 like Mac OS X; en-us) AppleWebKit/528.18 (KHTML, like Gecko) Version/4.0 Mobile/7A400 Safari/528.16)

    The Mac Pro has 8 RAM slots (4 per processor). You want to put RAM into the machine in pairs, so if you put a 1GB stick in slot 1 of processor A you need to put a 1GB stick in slot 1 for processor B. The 6GB is most likely either three 1GB or two 1.5 GB sticks for each processor leaving you with either 2 or 4 slots open.
     
  4. kornyboy macrumors 68000

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    #5
    Wirelessly posted (iPhone: Mozilla/5.0 (iPhone; U; CPU iPhone OS 3_0_1 like Mac OS X; en-us) AppleWebKit/528.18 (KHTML, like Gecko) Version/4.0 Mobile/7A400 Safari/528.16)

    If I would have read the title a little closer and not assume that you were talking about the 8 core model I wouldn't look stupid. Oh well, on the Quad Core model of the Mac Pro, you do not have to load the RAM in pairs. It is ok to leave 1 slot open. That's a darn good price for the RAM as well.
     
  5. VirtualRain macrumors 603

    VirtualRain

    Joined:
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    Location:
    Vancouver, BC
    #6
    The best amount of RAM for a 2009 Mac Pro is the greater of:
    - A multiple of 3 DIMMS (Quad) or 6 DIMMS (Octo)
    - What you need to avoid page-outs

    It's more important to have enough memory than top performing memory, but it's ideal to have both.

    My order of preference:
    1. 3x2GB
    2. 3x4GB
    3. 4x2GB
     
  6. whyrichard thread starter macrumors 68000

    Joined:
    Aug 15, 2002
    #7
    i think i'll get the 6 gigs from crucial...


    oddly enough, apple's website has a configuration for 8 gigs (2gigs x 4)

    Memory
    The quad-core Mac Pro supports up to 8GB of 1066MHz DDR3 ECC SDRAM memory in four slots. Choose more memory for improved overall system performance.
    Learn more
    Because accessing data from memory is much faster than accessing data from the hard drive, the more memory your system has, the faster it can manipulate your data. The result is greater application performance, especially when working with large files and memory-intensive applications such as graphics, audio, video, and scientific applications.

    The Mac Pro now uses 1066MHz DDR3 ECC SDRAM memory, an advanced memory technology that is not only fast, but also reliable. ECC provides this added layer of reliability by automatically correcting memory errors if they occur.


    3GB (3x1GB)
    6GB (3x2GB) [Add $150.00]
    8GB (4x2GB) [Add $250.00]
     
  7. quantum003 macrumors 6502a

    quantum003

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    #8
    I don't understand. Are you saying that you think the machine runs faster and stays healthier for longer using 6GB of RAM instead of 12GB? Or are you taking cost of the RAM into consideration when ranking those?

    I'm running 7GB in my 4-slot Mac Pro (2009). I was considering ordering 3x 4GB sticks and upgrading to 14GB, but your rankings seem to indicate that I'd be better off by taking out 1GB now?:confused:
     
  8. Dr.Pants macrumors 65816

    Dr.Pants

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    Jan 8, 2009
    #9
    :confused:

    What DIMMs do you have in there?
     
  9. quantum003 macrumors 6502a

    quantum003

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    #10
    They are Crucials... 3x 2GB and 1x 1GB in the 4th slot for a total of 7.

    If I bought the 3x 4GB kit I would put one of the 2GB I have now in the 4th slot for a total of 14GB.

    Does that sound like a wise move? Maybe I'm misunderstanding something.
     
  10. Genghis Khan macrumors 65816

    Genghis Khan

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    Location:
    Melbourne, Australia
    #11
    7GB in a quad-ore '09

    it's either

    a) 1GB, 1GB, 1GB, 4GB

    or

    b) 2GB, 2GB, 2GB, 1GB



    in the case of b) - yes, take out 1 GB .
    in the case of a) - WTF
     
  11. Genghis Khan macrumors 65816

    Genghis Khan

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    Location:
    Melbourne, Australia
    #12
    What you're probably missing is that Nehalem processors run on triple-channel memory...this means that each processor cycle runs through a maximum of 3 RAM slots at a time before moving on.

    Having 4 chips just slows it down unless you're max-ing out you're existing RAM.

    So yes...take out 1GB :p
     
  12. VirtualRain macrumors 603

    VirtualRain

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    Aug 1, 2008
    Location:
    Vancouver, BC
    #13
    I guess it might have been clearer had I mentioned that Nehalem CPU's have tri-channel memory controllers that run optimally with 3 DIMMS. Running 4 dimms slows the whole lot down to dual channel performance which isn't a real big impact, but as I say, why compromise speed if you don't have to?

    My order of preference is to maintain top performance while ensuring I have enough RAM. When 6GB is no longer enough, I would opt for 3x4GB before 4x2GB for this reason.
     
  13. quantum003 macrumors 6502a

    quantum003

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    #14
    Cool, thanks for the info. So, I do need to order the 3x 4GB kit and leave the 4th slot open for a total of 12GB.

    Thanks again guys, much obliged for the info.
     
  14. Tesselator macrumors 601

    Tesselator

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    Jan 9, 2008
    Location:
    Japan
    #15
    I think 6GB is too small so 8GB will show a speed increase in those situations where 6GB is not enough. For my uses under 10.5.x that's very many indeed. To me the question is 8GB or 12GB. 12GB will give you the triple-channel mode and at the same time usually be enough. 8GB I could maybe see if there was a strict budget.
     
  15. alphaod macrumors Core

    alphaod

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    Feb 9, 2008
    Location:
    NYC
    #16
    If you need the extra RAM provided by the extra stick, the benefit of that extra RAM will exceed any loss in performance. That said dual channel performance is plenty for most cases.
     
  16. ManiG macrumors member

    Joined:
    Aug 11, 2009
    #17
    I'm in the exact same situation. I'm sticking with 6g for now, but if I notice recurrent pageouts, I will plug in the extra 1g for a total of 7g and see if that solves the problem.

    Don't worry too much about triple channel vs single channel performance. For 99.9% of people, the difference in overall system performance will be 1-2%. So if 7g of ram does it for you, then you're good.
     
  17. parakiet macrumors regular

    Joined:
    Nov 23, 2008
    #18
    @ owc: 12gig in 3 * 4 => $479.99
    @ crucial 12 gig in 3 * 4 => US $1139.99


    that difference is huge!
    any ideas why?!?:eek:
     
  18. Dr.Pants macrumors 65816

    Dr.Pants

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    Jan 8, 2009
    #19
    This from OWC?

    The difference is from Crucial I would assume one is getting the matched set, and from OWC one is getting more then one module.

    I think?....
     
  19. Nater macrumors newbie

    Joined:
    Sep 5, 2009
    #20
    It depends, if you absolutely need 8GB of ram then it's the only choice. However, configurations that aren't in multiples of three are less than ideal Any Nehalem chip, be it a Core i7 or Xeon, is supposed to have it's ram installed in sets of three. Installing 8GB will revert it to dual channel operation. It's not a big performance hit, you'd probably not notice.

    Still, the MP should have the ability to do 12GB or more with six DIMM slots. The X58 chipset supports 24GB of non-registered, non-ECC ram. And honestly, that's the kind of ram you should use. There is really no benefit for you running ECC registered ram.
     
  20. Umbongo macrumors 601

    Umbongo

    Joined:
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    Location:
    England
    #21
    More likely there is little demand for it and they price it accordingly. Their registered DDR3 memory in 4GB DIMMs is of a similar price to OWC, yet would cost more to manufacture if produced in the same quantities.
     

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