would one 8GB stick of RAM be o.k. for 6-core?

Discussion in 'Mac Pro' started by malch, Aug 20, 2010.

  1. malch macrumors 6502

    Jan 20, 2008
    Hi, I'm pushing the envelope to buy the new 6-core, so I'm hoping to wait on adding a lot of RAM until 1. I can save up some more money and 2. Avid makes use of more RAM (right now it's limited).
    Given that some day I'd like to have a lot more RAM, I'd like to put just one 8GB stick in now (rather than filling slots with smaller sticks that I'd end up having to throw out if I eventually want to go 8GB sticks all the way) — is this o.k., though?
    Is just one stick of RAM going to work?
    (from my limited understanding of these 8GB sticks, they don't work with anything else, so I can't leave the stock 1GB sticks in).
  2. wywern209 macrumors 65832


    Sep 7, 2008
    do you rly want to know?
    this link seems to say its fine so it should work. You will lose dual channel boost though that is minimal maybe a 1-2% effect as to using 2 x 4gb sticks. Each Ram slot does support up to 8gb of ram so you are fine there. just keep in mind that it needs to be ECC ram.
  3. philipma1957 macrumors 603


    Apr 13, 2010
    Howell, New Jersey
    along with the same idea if I buy the base 4 core 2.8 with the better graphics card would 1 8gb stick alone work? I guess I could test by trying to run the machine with 1 1gb stick. iMac and mac mini let me run 1 stick but I don't use ecc ram with them.
  4. TheBritishBloke macrumors 68030


    Jul 21, 2009
    United Kingdom
    Wait for OWC to test it out.. They said they'd test it once they get their machine.
  5. Giuly macrumors 68040


    What's wrong with 4x4GB, which would run in triple channel, and cost together $632?
  6. malch thread starter macrumors 6502

    Jan 20, 2008
    My thinking is that if I add 4X4GB then, yes, I'll be in great shape—16GB—for now, but not at the 4X8GB (32GB!) peak that I might get to, some day, if I go for the 8GB.
    I'm buying this Mac Pro for the long haul. When the rest of you are going to be busy upgrading to Sandy Bridge or whatever, I'm not even going to allow myself to read the "New Mac Pro" threads. If I get this machine for $4,000 and change, it's going to have to last me for five years.
    Regards, malch
  7. reel2reel macrumors 6502a


    Jul 24, 2009
    I'm buying 8 GB sticks for that very reason. I'd just call OWC and ask them about the single 8 GB. You can contact them via chat in their support area, too:

  8. malch thread starter macrumors 6502

    Jan 20, 2008
    thanks very much. I really appreciate the advice people are so generous with on this forum... I'll call them in the morning.
    cheers, malch
  9. Ryan P macrumors regular

    Aug 6, 2010
    Geez....this is going to make me want to populate my dual processor system 1 8GB at a time all the way up to 48 GB.....the insanity!!
  10. brentsg macrumors 68040

    Oct 15, 2008
    At least people will know what to give you for holidays .. for quite some time. ;)
  11. deconstruct60 macrumors 604

    Mar 10, 2009
    Is is unlikely that it would be a minimal lose of only 1-2%. That would only be true if your benchmark was primarily disk I/O bound anyway.

    The triple versus alternative ( either triple + no interleave or two dual interleave ... depending upon what firmware told the Xeon do when using 4 slots ) interleaves at least had some interleave somewhere. Going to a solitary DIMMs means you have no interleave. You are reverting to pre-Nehalem single front side bus architecture. That sucks. All the benchmarks where the Nehalem processors stomp the 2008 ( and earlier ) configs support that.

    If the price point on 8GB are not affordable then don't buy them. Use two 2's or 4's. So that minimally buy in pairs unless just stuffing the sole remaining empty slot. Take the extra money would have spent on 8's and put it toward buying better disk I/O at some point. That will have a bigger bang for the buck for vast majority of folks after get out of the "minimal" memory config the boxes ship with.

    Using 3 x 1GB plus the one 8GB would be better than just one 8GB all by its lonesome. OWC's 8's won't play together like this though. Crucial's may but Apple's may not.
  12. 2contagious macrumors 6502a


    Apr 29, 2008
    what's that based on? (how do you know if a certain 8GB ram stick works together with the three 1GB sticks?
  13. MacSince1985 macrumors 6502

    Oct 18, 2009
    Definitely wait and see what OWC's tests reveal. Intel says that processor is limited to 24Gb (6x4Gb) and Apple lists that Mac as 16Gb max. Some rumors claim that the 8Gb module will not work at all.

    Remember when 8Mb RAM cost $1000+ and there was heavy security around all the memory booths at MacWorld? Memory is so cheap now by comparison.
  14. 2contagious macrumors 6502a


    Apr 29, 2008
    didn't they already confirm?
  15. MacSince1985 macrumors 6502

    Oct 18, 2009
  16. Umbongo macrumors 601


    Sep 14, 2006
    No 8GB DIMMs will work with any other DIMMs that are branded as "Mac Pro memory". This is because Apple only support unbuffered ECC so this is what companies sell, but 8GB DIMMs are only available as registered ECC making them an exception.
  17. malch thread starter macrumors 6502

    Jan 20, 2008
    Thanks deconstruct60 and umbongo: I now gather that yes, I can use one 8GB stick, BUT:

    - the Apple RAM (that ships with the Mac Pro) WON'T work with the OWC 8GB RAM, because the OWC RAM is buffered (or 'registered'; I'm not familiar with any of this terminology, but as long as I know what works and what doesn't, I'm o.k.), so no, adding an 8GB OWC stick to the 3 1GB sticks that ship with the machine will not give me 11GB of RAM,


    - things won't run as fast with just one 8GB OWC stick filling just one slot, because of "interleaving" issues.

    Have I understood this correctly?
    thanks, malch
  18. Umbongo macrumors 601


    Sep 14, 2006
  19. Icaras macrumors 603


    Mar 18, 2008
    California, United States
    I just chatted with an OWC representative and he told me that DIMMS had be in 2, 4, 6, or 8 sets. So according to him, just using one DIMM won't work.
  20. malch thread starter macrumors 6502

    Jan 20, 2008
    I'm going to have to bite the bullet and get two 8GB sticks...
    thanks again for the help.
  21. milo macrumors 604

    Sep 23, 2003
    I think it's very risky to buy 8 gig chips with the intention of adding more later. The 8's seem to be extremely particular about what they are used with - if you don't buy all the 8's at the same time, there's a chance they may not play nice together, making one or more of them unusable. Chips bought later may list the same specs but still not be compatible, it happens sometimes.

    If you are OK with starting with 8 gigs, I'd probably just use 2x4 or 4x2. You may end up dumping those chips later but depending when you get them the price of the 8 may have dropped enough that it ends up being cheaper to just buy chips now and dump them (or trade in if you can) later.

    Four chips won't run in triple channel, only when there are three slots used - other combinations supposedly drop down to single channel although that is supposed to be minimal difference for the user.
  22. jenzjen macrumors 68000

    Aug 20, 2010
    Just a correction for #19, I received my hex and only ordered 1 8Gb module from OWC.

    The 8Gb alone does in fact work ... what doesn't work is leaving the 2x1Gb Apple OEM modules + OWC 8Gb module ... when I did this, the MP would not boot up & instead got a flashing white power button light.
  23. sboerup macrumors 6502

    Mar 8, 2009
    I ordered 2x8GB fron Transintl.com today, get everything tomorrow and will test.
  24. barefeats macrumors 65816


    Jul 6, 2000
    I tested the 3.33GHz 6-core with two different memory configs. Then I ran a 64 bit memory stress test.

    4x8G = 32G = 10.5 GB/s
    3x8G = 24G = 14.3 GB/s (or 36% faster)

    However, when I ran After Effects CS5 project render using 12 cores and 1.5G per core, the 32G config took 72 sec, the 24G took 71 sec. In other words, if there is a difference in real world performance, you would need a stopwatch to detect it.

    Why? Because few if any real world apps use the full memory bandwidth. I'm still testing. If I find any app that benefits from the 3 stick "triple channel" config, I'll report it here.
  25. hispanicboy macrumors newbie

    Jul 31, 2010
    I am running a Quad 3.2 with 1 stick of 8GB from OWC.

    No problems at all.

    (In fact when I first booted it up after taking out the 3 1 GB sticks and replacing them with my 1 8GB stick I got a message saying that my RAM was installed in the proper slot.) :)

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