Yet another 2010 Mac Pro RAM question

Discussion in 'Mac Pro' started by brentsg, Feb 16, 2011.

  1. brentsg macrumors 68040

    Oct 15, 2008
    I've searched but not been able to find the answer to this one.

    Can anyone confirm that a 2010 6-core Mac Pro will run RAM at 1333 when all 4 slots are filled?

    I had 12GB of OCZ modules running fine at 1333, but I was having some page-outs. I obtained a matching 4GB module and installed that today. My RAM immediately dropped down to 16GB at 1066.

    Is this working as intended? Yes, I realize there are bandwidth implications with tripple-channel, etc. I just didn't expect it to manifest like this.

  2. philipma1957 macrumors 603


    Apr 13, 2010
    Howell, New Jersey
    it has to do with ram structure thee was a post on 16gb sticks that mentions 4 level or 4 stage ram this type will down clock with 4 sticks in the 2010 mac pro
  3. brentsg, Feb 16, 2011
    Last edited: Feb 16, 2011

    brentsg thread starter macrumors 68040

    Oct 15, 2008
    I think I eventually found my answer here:

    Cliff notes, it's normal I think.

    Edit: Then again, that post later mentions that Westmere CPUs were tweaked to allow all banks to fill in "some configurations" and still use 1333. The more I read the more confused I become.
  4. Umbongo macrumors 601


    Sep 14, 2006
  5. nanofrog macrumors G4

    May 6, 2008
    Yes, this is normal.

    To maintain 1333MHz means 1x DIMM per channel, so once you add another DIMM on one of the channels, it will drop to 1066MHz.

    Now as most software cannot utilize the bandwidth of the memory controller architecture of Nehalem/Westmere, don't worry about it. :eek: Capacity trumps frequency in most cases (exceptions are recursive algorithm based software, which is rare; engineering and scientific based software is where you may encounter applications that use this). :)
  6. brentsg thread starter macrumors 68040

    Oct 15, 2008

    Yeah, sadly my scientific days are in the rear-view mirror. Nowadays it's all about running a whole bunch of virtual machines at the same time.

    Really 12GB was a lot, but in some cases I could feel it start hitting the drive and I could verify this via the activity monitor.

    This machine is really a beast with VMs when configured well.

    Wow, I'm also full of crap. I'm using Crucial modules, not OCZ. I had that SSD thread on my mind when I posted.
  7. nanofrog macrumors G4

    May 6, 2008
    The brand won't make a difference, as it's governed by Intel's memory controller design. ;)

    If you're paging out for your VM configuration, you'll either have to add more memory (means you'd need 8GB sticks, which most are RDIMM <R = Registered; and will not work with your existing memory non-ECC or UDIMM's <U = Unbuffered BTW>, or scale back the VM's memory allocation (not sure what Crucial memory you're running - UDIMM or non-ECC, which is what you usually find, as it's more common due to consumer grade systems, such as gaming or general purpose systems).
  8. brentsg thread starter macrumors 68040

    Oct 15, 2008
    Yeah, I just felt compelled to correct my mistake.

    I was paging at 12GB, should be fine now. I'm just using the non-ECC modules. I don't need ECC.

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