6-Core Ram upgrade question

Discussion in 'Mac Pro' started by Zapallar, Sep 17, 2010.

  1. Zapallar macrumors newbie

    Joined:
    Sep 2, 2010
    #1
    So, having just ordered my 6core Mac Pro i'm stuck with the mandatory RAM upgrade ... I'm planing on something in the 16GB department ... so 4x4GB would be my first choice. Now reading all the posts here I'm quite confused wether this is the right choice:

    - Three 4GB modules would give me the tripple channel benefit ... would adding a fourth 4GB module (making the total of 16GB) harm the performance (bus speed, etc) as it's "an extra module"?

    - Kingston offers ValueRam PC3-10667R .... which is different from the DDR3 PC3-10600 other Mac-specific shops offer. Would the Kingston RAM work in my Mac Pro?

    and no ... my budget is rather limited so three 8GB modules are a no-go :(

    Thanks a lot guys!!
     
  2. Honumaui macrumors 6502a

    Joined:
    Apr 18, 2008
    #2
    get your memory from http://www.transintl.com/store/category.cfm?Category=1

    dont worry about the 4 or 3 its not going to really make any real world difference and in your case ? depending if the computer needs more ram that will make it quicker :) than any bit you may loose other times

    yes 3 is better www.macperformanceguide.com did a test on it ? if you want actual numbers but again dont worry

    the difference between 4 4 gig sticks and 2 8 gig sticks is not much to future proof yourself though usually about %10 ? and something I would think about depending on what you do with your mac :)
     
  3. Sun Baked macrumors G5

    Sun Baked

    Joined:
    May 19, 2002
    #3
    Last I looked (when Apple switched to this configuration) it looked like Apple was keeping triple channel in most cases -- Unless you intentionally downgraded to 2 DIMMs.

    With the 4th module sharing the 3rd modules memory channel, with it switching between the two when needed. Not downgrading you to dual channel, so the loss being the time it takes the machine to switch DIMMs to make whichever DIMM in slot 3-4 it needs.

    There is a higher latency for 4th memory slot.

    But this still beats the pants off resorting to using the HDD for memory space.
     
  4. reel2reel macrumors 6502a

    reel2reel

    Joined:
    Jul 24, 2009
    #4
    OWC is awesome, too. Fast ship and good prices. Love the way they pack stuff, too, which is important with expensive electronics.

    Got 3 x 8GB for my Hex and the Mac seems to love it. Snappiest computer I've ever used and I don't even have my SSD installed yet.
     
  5. Honumaui macrumors 6502a

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    Apr 18, 2008
    #5
    I got my ram this time from trans ? and it was not packed as nice ? but was quite a bit cheaper

    usually buy everything from owc though
     
  6. xgman macrumors 601

    xgman

    Joined:
    Aug 6, 2007
    #6
    This is not the case. I confirmed this with a high level Apple tech and also with Intel engineers and also Micron for good measure. If you populate all 4 slots, it reverts to single channel mode. The best way to configure a six core mac pro and ensure triple channel mode is to use only the first 3 slots. Either 3x4 for 12 GB or 3x8 for 24GB which is what I ended up doing.
     
  7. reel2reel macrumors 6502a

    reel2reel

    Joined:
    Jul 24, 2009
    #7
    I noticed trans has some amazing prices!
     
  8. you39 macrumors regular

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    Mar 21, 2010
    #8
  9. philipma1957 macrumors 603

    philipma1957

    Joined:
    Apr 13, 2010
    Location:
    Howell, New Jersey
    #9
    value ram in theory is more likely to break due to lower cost parts that make the stick up.
     
  10. chrmjenkins macrumors 603

    chrmjenkins

    Joined:
    Oct 29, 2007
    Location:
    CA
    #10
    Any serious brand offers lifetime warranty on all of its sticks.
     
  11. you39 macrumors regular

    Joined:
    Mar 21, 2010
    #11
    The point is: I haven't seen equivalent parts at one vendor so far, but the vendors that had System Specific Memory sold it for less than those who sold Value Ram... :confused:
     
  12. leftPCbehind209 macrumors member

    Joined:
    Aug 23, 2010
    #12
    If you go 2 x 8gb sticks, do you leave in the 2 x 1gb sticks it comes with too?


    ^^^^^^^^^^^^
    (for total of 18gb)
     
  13. Honumaui macrumors 6502a

    Joined:
    Apr 18, 2008
    #13
    one thing that was interesting I was playing with the ZDNet overclocking tool and could not get good results ?
    after some forums and research it seems the people that had the best results had apple ram ! and the worst was OWC ram ? the ones that did inbetween are using transintl memory ?

    kinda strange but ya never know :) no way to test it but figured others use trans and have had good results and its not just a few bucks but well over hundred I saved ?
     
  14. Sun Baked macrumors G5

    Sun Baked

    Joined:
    May 19, 2002
    #14
    Look at some of the numbers maxing out the memory provides a boost.

    Using 3 slots might be 15% faster, but 4 slots don't exact the penalty for single channel you are talking about (your example would make 4 slots operate at a 1/3 of the memory speed).

    If you don't have enough memory, the penalty is far higher than the 4th DIMM.

    The last 2 slots shares a single channel, in the past Apple has used switching technology to share channels (the FB-DIMM machines before the 2009 Mac Pro used had 2 switched DIMMs on every memory channel).

    The current machine design is simply an odd duck with 2 dimms only sharing 1 of the memory channels. Are you sure those people actually knew that the tests don't support them.

    http://blog.macsales.com/672-2009-mac-pro-nehalem-initial-speed-tests
     
  15. leftPCbehind209 macrumors member

    Joined:
    Aug 23, 2010
    #16
    If you go 2 x 8gb sticks, do you leave in the 2 x 1gb sticks it comes with too?


    ^^^^^^^^^^^^
    (for total of 18gb)
     
  16. Sun Baked macrumors G5

    Sun Baked

    Joined:
    May 19, 2002
    #17
    Follow Apple's memory guide for adding 2 DIMMs making sure that the big DIMMs don't go onto the shared memory channel.

    Basically remove the 2 1Gb dimms, stick the 8GB dimms in their place, and move the 1GB dimms to the unused shared memory channel.

    Then run the /system/Library/CoreServices/Memory Slot Utility.app to make sure you got it right. (think the path is something like that)
     
  17. malch macrumors 6502

    Joined:
    Jan 20, 2008
    #18
    Quick question. It would be a real stretch for me to buy 3x8 sticks of RAM, which at OWC is selling for $1,012
    (for comparison: three 4GB sticks are $395).

    BUT... I like the idea of adding more RAM at a later date, when I can afford it, and with this in mind, I'd rather have 8GB sticks, and I'm wondering two things:
    1. how much am I hurting my speed if I put just two 8GB sticks in for now (I know this breaks the 3-slot rule) instead of three 4GB sticks?
    and
    2. Joe at OWC told me in an email that "we purchase our 8GB in volume; they are all matched pairs and will always work together".
    That's fine and dandy. But what if I do end up buying another 8GB stick a year from now? It wouldn't be working with its "pair". Is that a worry?

    thanks for any advice,
    malch
     
  18. philipma1957, Oct 7, 2010
    Last edited by a moderator: Nov 11, 2010

    philipma1957 macrumors 603

    philipma1957

    Joined:
    Apr 13, 2010
    Location:
    Howell, New Jersey
    #19
    I am not sure about the first q. my gut tells me it would not be a problem unless you are using a real ram hog problem.

    the second question the answer is waiting a year may mean you will get non-matching ram.

    I grabbed 12 gb ram at a good price about 10 days ago around 300 it was the 1066

    it is 91 a stick and the discount code is BAT5 so 273 minus 5 is 268 plus shipping about 280. spending 280 for x 4gb =12gb now and waiting til june to get a good 8gb a stick price may work for you

    here is my thread on my ram buy http://forums.macrumors.com/showthread.php?t=1020241&highlight=

    one last link this ram below is samsung in theory it would work in a mac pro it is 226 a stick about 680 for 3 sticks after shipping and the small discount.
    this is wrong
    I miss clicked forget this link
     
  19. malch macrumors 6502

    Joined:
    Jan 20, 2008
    #20
    Hi Philip,
    Very nice of you to post all these urls. Much appreciated. I have to ask, though, about your above quotation. I was under the impression (mistakenly?) that you shouldn't mix different configs of RAM. In other words, if I buy 4GB sticks now, I shouldn't pop in an 8GB stick later.
    That's why I'm thinking if I want, some day, to end up with lots of RAM, I should start now with two sticks of 8. If I start off with the more affordable 4GB variety, it limits me down the road.
    What do you think?
    Thanks again, malch
     
  20. philipma1957, Oct 7, 2010
    Last edited by a moderator: Nov 11, 2010

    philipma1957 macrumors 603

    philipma1957

    Joined:
    Apr 13, 2010
    Location:
    Howell, New Jersey
    #21
    lazy writing. because the post was long. a good price for 8gb stick in june should read a good price for three 8gb sticks in june.

    I forget that I sell off a lot of gear. I know that 12gb will be enough for me.

    In your situation I would buy the 12 gb from superbiiz now and then sell them on ebay in the spring. The plus is I have 12gb now for about 280.

    If I buy the pair of 8gb sticks from owc they are 678.

    So out of pocket I am 280 vs 678. There would be some cases that the 12 gb is better then the 16gb or the 16gb would be quicker then the 12gb, but more often then not the difference would not be much. I would get to hang on to 400 bucks.

    I would also avoid the problem that the 8gb sticks from owc get changed in the spring. THIS WOULD DRIVE ME NUTS!

    But I look at it from a user/reseller viewpoint not a user viewpoint. I buy and sell on ebay all of the time. I know that in the spring I could sell the 3 sticks as mac pro ram. If the owc go out of stock and I can't add a stick selling 2 sticks on ebay will be hard. Buyers will want the third stick for their mac pro.

    the below is wrong: I had the wrong link for 8gb ram the 8gb is out of stock
    .*************************************************************
    I would also be very tempted to try the 8gb sticks I linked at superbiiz.

    3 times 8gb is 24gb right here right now my cost would be about 680 same as two sticks from owc. If they don't work in the pro I could sell them on ebay or return them. they are a brand name samsung and they are selling for over 300 in a few other stores.
    *************************************************************
     

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