Mac Pro 2010 8GB ram configs?

Discussion in 'Mac Pro' started by iondot, Aug 26, 2010.

  1. iondot macrumors member

    Joined:
    Jun 30, 2008
    #1
    I'm about to order the 3.33 hexacore Mac Pro and money is tighter than I would like. It is feasible to put in only a single 8GB stick? Can I put in just two?

    I know three is theoretically ideal, but for now can I get away with less and, if so, what sort of performance hit would I be looking at with one or two sticks?
     
  2. Umbongo macrumors 601

    Umbongo

    Joined:
    Sep 14, 2006
    Location:
    England
    #2
    You can use any number of DIMMs.

    If we say three DIMMs give you 100% bandwidth performance, two give around 80% and one gives around 45%.

    If using 1333MHz DIMMs the difference between three and four is around 30-35% less. That is due to the limit of 1066MHz memory speeds with registered DIMMs when using more than one on a channel and the drop to a dual channel type interleave.

    The real world performance impact can be negligible however, so if you are planning to add more in the near term then I would buy what you can afford and not worry too much.
     
  3. xgman macrumors 601

    xgman

    Joined:
    Aug 6, 2007
    #3
    Only if you plan on upgrading to 3 8gb sticks later. Otherwise you would get better performance with 3 smaller sticks.
     
  4. iondot thread starter macrumors member

    Joined:
    Jun 30, 2008
    #4
    So if I bought one 8GB stick, would my computer run at 45% the speed it would if there were three? That would be beyond my ability to accept.
     
  5. Umbongo macrumors 601

    Umbongo

    Joined:
    Sep 14, 2006
    Location:
    England
    #5
    Your memory bandwidth would be 45% of what it would be at triple channel. Real world performance? I couldn't say. The difference between 2, 3 and 4 DIMMs for real application usage is often negligible. Real world between dual channel and single were always very close back in the DDR2 days too. I wouldn't worry about it, it won't cripple your system, it just isn't optimal for memory intensive usage.
     
  6. ahavriluk macrumors member

    Joined:
    Aug 23, 2010
    #6
    Is it OK to use different size sticks? Let's say 4, 4, 1 or 8, 1, 1 Gb sticks or any comdination of 4 or 8 Gb sticks?
     
  7. iondot thread starter macrumors member

    Joined:
    Jun 30, 2008
    #7
    @Umbongo - I really appreciate your help here.

    I'll be using my machine mostly for work in Photoshop on RAW files from my 5Dii. I know Photoshop can be memory sensitive. Would the single 8GB stick be hobbling me in that particular scenario?
     
  8. iondot thread starter macrumors member

    Joined:
    Jun 30, 2008
  9. Umbongo macrumors 601

    Umbongo

    Joined:
    Sep 14, 2006
    Location:
    England
    #9
    The 8GB DIMMs are registered memory and so can only be used with other registered DIMMs. 1GB, 2GB and 4GB DIMMs that are certified for the Mac Pro are all unbuffered. You could use non-certified registered DIMMs of other sizes though.

    I'd go for at least two. I couldn't say what your real experience would be between, say, 1x8GB vs. 4x2GB, but it is far from the ideal performance that can be attained. If you are thinking about buying another in a month or so then I'd just go with one now.
     
  10. mrbard macrumors newbie

    Joined:
    Apr 5, 2007
    Location:
    Norway
    #10
    So is there a performance impact if you mix registered with unbuffered RAM? Will you have memory problems, or?
     
  11. 2contagious macrumors 6502a

    2contagious

    Joined:
    Apr 29, 2008
    Location:
    UK
    #11
    I think it just plain doesn't work, not sure though :confused:
    Anyway, this might be of interest to you:


     

Share This Page