RAM configuration advice

Discussion in 'Mac Pro' started by ithinkitsnice, May 28, 2010.

  1. ithinkitsnice macrumors member

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    #1
    I've just ordered a new quad core MP from apple with the minimum 3GB RAM option, with a view to upgrading the RAM immediately to 8GB (2x 4GB) from Crucial.

    My question is what to do with this 3GB I've got spare? I was always prepared to live without it as the Crucial upgrade is the best balance between cost and leaving slots free for future upgrading (I plan to add another 8GB as soon as I can afford to)

    Can I fill up the two free slots with a couple of the 1GB sticks I have left over in the meantime? If I can, is this wise? I understand RAM should be installed in matching pairs or threes for optimum performance, but does having 10GB v 8GB offset the performance hit?

    The machine will be used for 80% 2D graphics/illustration (often very large, multi-layered Photoshop files) and 20% video/animation (mainly After Effects 2.5D work)

    Thanks for any advice
     
  2. Hellhammer Moderator

    Hellhammer

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    #2
    Yes, you can use the 2x1GB to fill the remaining slots. No need to install RAM in pairs.
     
  3. VirtualRain macrumors 603

    VirtualRain

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    #3
    The memory controller on the Nehalems, can run in single, dual, or tri-channel mode. In dual or tri-channel mode, data is interleaved/stripped across the memory channels like drives in a RAID0 array. It provides benefits in read/write performance.

    To gain the performance benefits of dual or tri-channel operation, you need to have identical and only identical DIMMS in the respective 2 or 3 slots. If you populate all four slots with a mixed-bag of DIMMS, it will work, but it's hard to say how much performance you will get as some amount of memory may allow interleaving and some none.

    If I was you, I would first consider replacing the 3x1GB sticks with 3x2GB or 3x4GB sticks for tri-channel performance. However, if that's not viable for you, then 2x4GB or 4x2GB will provide the same dual-channel performance.
     
  4. Hellhammer Moderator

    Hellhammer

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    #4
    Dual-channeling will provide about 5% increase in performance when doing memory intensive tasks so IMO it's pretty useless, tri-channel might provide something like 8%. I wouldn't worry about channeling, they are more or less a marketing scheme
     
  5. Apple Corps macrumors 68030

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    #5
    I would NOT touch Crucial ram at their current inflated prices. Go OWC - I just did 16 GB upgrade with four 4GB modules at close to 1/2 the $$ Crucial is charging.

    I used to purchase exclusively from Crucial.
     
  6. VirtualRain macrumors 603

    VirtualRain

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    #6
    Agreed, my mantra is first, ensure you have enough memory and then second, optimize it for performance. The corollary to which is, don't just plug up your DIMM slots without considering the performance impact, especially if you don't need that extra memory.

    With slots populated with 4GB, 4GB, 1GB, 1GB DIMMS... does anyone know what the IMC is going to do with this? It could very well default to single-channel operation which will impact performance.
     
  7. Hellhammer Moderator

    Hellhammer

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    #7
    As long as the 4GB and 1GB modules are in matched slots, both can take advantage of dual-channeling. E.g. 4GB modules in yellow slots and 1GB modules in blue slots (don't know what colors does the Mac Pro have but I hope you got the idea:cool:). Due that, it can be useful to use e.g. 6x1GB instead of 3x2GB (again generally, not talking about Mac Pro slots but this same applies to MP as well)
     
  8. ithinkitsnice thread starter macrumors member

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    May 27, 2010
    #8
    I'm in the UK, but I'll consider OWC. Depends on shipping and the risk of HMRC skinning me for even more once it lands. But that's another issue.

    I will eventually get it to 4x4GB which is why I'd purchase 2x4GB for now. Putting these 'spare' 1GB sticks would just be an interim measure of convenience, provided it was worthwhile.

    Am I right that each distinct pair (4/4 & 1/1) will each work in dual channel mode then?

    edit: just read this on OWC
    :confused:
     
  9. ithinkitsnice thread starter macrumors member

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    #9
    and now this...
    ...surely I can put 2x4GB in?
     
  10. Hellhammer Moderator

    Hellhammer

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    #10
    If you buy 4GB OWC modules, you cannot use other that those modules, it has something to do with their design. I haven't heard that other manufacturers have this issue so you should be fine as long as you avoid OWC in this case
     
  11. VirtualRain macrumors 603

    VirtualRain

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    #11
    You can definitely run 2x4GB and get dual channel mode performance.

    As Hellhammer points out, the OWC modules don't play well with others, so if you go that route, you need to use their modules exclusively.

    What we don't know, is how the memory controller operates with a mixed bag of DIMM's. It may combine channels A/B and interleave with C or it may default to single channel mode. It's hard to know. However, on page 47 of the manual, it states this...

    When I run it, (in my 3x2GB config), all I get is this, which may not be all that helpful...
     

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  12. Apple Corps macrumors 68030

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    #12
    Look at the price differences for heaven's sake :eek: You can populate with way more OWC ram and sell or toss the stock 1 GB modules.
     
  13. Hellhammer Moderator

    Hellhammer

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    #13
    OWC also has trade-in policy ;) They pay you 9$ per module if I recall correctly
     
  14. ithinkitsnice thread starter macrumors member

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    May 27, 2010
    #14
    For the benefit of anyone else thinking of importing from OWC to the UK, the intentional shipping isn't too bad (starting at just under $15) and I've just discovered that DIMMs are 0 rated for import duty to the EU. The taxman will still want 17.5% VAT (if he finds them), although I can claim that back as this is a business purchase. Looks like I can get 3x4GB for only a little more then I can get 2x here.

    So I reckon I will do that. Thanks. :)

    I don't think the trade in will be worth the postage though ;)
     
  15. Apple Corps macrumors 68030

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    #15
    I also think the trade in is a joke - not worth the time or postage. As mentioned, I just loaded my new Mac Pro with 16 GB OWC - who knows, under all the labels might be Micron chips anyhow :D

    Also - go to Utilities > Activity Monitor > System Memory and check your pages in/outs. If you have few, then you are not memory constrained and could give a little (very little) thought to the multi channel improvements.

    OTOH - if you see pages in/outs then more ram is in order - that is telling you that there is not enough ram and the hard drive is being used as "virtual memory".
     
  16. ithinkitsnice thread starter macrumors member

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    May 27, 2010
    #16
    Oh I'm sure I am paging right now. I'm still sitting here on my 3 year old iMac until this thing arrives on Thursday, and probably longer until all the 3rd party bits arrive :impatient:
     
  17. Apple Corps macrumors 68030

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    #17
    Gotcha - I'm sure you will be impressed with your new Mac. The internal organization is so clean and upgrading is a no brainer.

    I thought I had most everything organized but it has taken more time and effort to reload many things, updates, upgrades, will be glad to have it wrapped up soon.
     
  18. Fomaphone macrumors regular

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    Jan 11, 2009
    #18

    i got my RAM from overstock.com, which has cheaper shipping than OWC and a lower price on mac pro RAM from kingston. this weekend there's even at 15% off coupon sitewide.

    also, hang on to your apple RAM. you will need it for apple care service and also for your own troubleshooting if something goes wrong.
     

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