MP RAM: 2x2GB or 4x1GB?

Discussion in 'Mac Pro' started by maberga29, Sep 21, 2007.

  1. maberga29 macrumors member

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    #1
    I've searched google and this forum and can't find a definite answer:

    MP: 3GHz Quad Core Xeon.
    I'm trying to figure out if there is a big (noticable) difference in speed between upgrading RAM with less of a bigger size (2x2GB) or more of a smaller size (4x1GB). I realize that both the 2GB and 1GB chips are still 667 MHz, so my instinct tells me the 4x1GB setup will be able to handle a larger load (since it has 4 chips at 667 vs. 2 at 667). Does anyone know with greater certainty? Also, with the quad core processors, is there a benefit to having 4 separate chips?
     
  2. Mackilroy macrumors 68040

    Mackilroy

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    #2
    2x2 Gb means that (unless you want 32 Gb of RAM) that you can max out the Mac Pro without paying through the roof. You're supposed to add RAM in pairs, and I think theoretically 4x1 Gb is supposed to run faster, but I don't recall for certain.
     
  3. bmcgrath macrumors 65816

    bmcgrath

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    #3
    Yeh get 2*2, if you wish to upgrade in the future it means you have more availble slots to add extra ram ;)
     
  4. maberga29 thread starter macrumors member

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    #4
    I'm not too concerned with running out of slots. I don't think I'll have to max out the RAM... plus even with 4x1 (plus 1 from apple), that still leaves room for a total of 13GB.

    I think so too, but am no more certain. It would be interesting to know if if our suspicions of cause and outcome are right about this. Has anyone seen any RAM config benchmark tests? It doesn't have to compare this specific case.
     
  5. ivi7 macrumors 6502a

    ivi7

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  6. Multimedia macrumors 603

    Multimedia

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    #6
    Only Buy 2GB Pairs For Only $238 Per Pair Total 4GB @ $59.50 Per GB

    2x2 cost LESS than 1x4 plus it saves slots. You are foolish to even ask the question. There is virtually no performance hit for any mix when you follow this chart's guidelines.

    It is UNWISE to by less than pairs of 2GB sticks ALWAYS.

    Link to $238 for the pair at Omni Tech via Ramseeker.com. Excellent ram at a fraction of other's prices. We're down to $59.50/GB

    Have you studied the chart on how to install all mixes of ram?
     

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  7. maberga29 thread starter macrumors member

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    #7
    Thanks for the chart, I hadn't seen it. Do you know of any tests or references to support your "no performance hit" statement?
     
  8. Multimedia macrumors 603

    Multimedia

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    #8
    "Hit" Myth Has Been Posted Here Numerous Times

    This topic has been posted to death. I've read it scores of times that any "hit" is nominal.
     
  9. netnothing macrumors 68040

    netnothing

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    #9
    Multimedia....have you ordered RAM from Omni Tech before? And are you using it now? Price looks good compared to places like Crucial.

    -Kevin
     
  10. /\/\ macrumors regular

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    #10
    @maberga29

    I am not sure, but I think you have a better performance with the 4 x 1GB.

    Because:

    So if you have only this 4GB, it would be better with 4 x 1GB RAMs.

    Marcus
     
  11. suneohair macrumors 68020

    suneohair

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    #11
    I would disagree. You have the stock 2x512MB + 2x2GB, making 4 sticks. You also have more room for expansion at that point. 4x1GB is impractical as it costs more, hinders expansion, and offers no real advantage in speed.
     
  12. /\/\ macrumors regular

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    #12
    ok you are right! my fault!

    I thought there was only the option between 2 x 2GB and 4 x 1 GB. ;)

    But 2 x 512 + 2 x 2 is of course the better way.
     
  13. Hennesie2000 macrumors 68000

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    #13
    4 x 1 will get you the 128bit processing where as 2 x 2 will only be 64bit.

    You are supposed to add ram in matched pairs as well due to the configuration. When I first got my mac prop i only got 1GB of ram (2 x 512) which only enabled 64bit channeling. Add and additional 1GB (2 x 512) made and amazing difference. Also pay attention to the way you are supposed to install the ram and into which dimm slots. That info is located on the inside of the computer case door.
     
  14. djhspawn macrumors member

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    Sep 15, 2006
    #14
    I read through this and am still not able to decide what I should do..

    I currently have 4 x 512, I want to upgrade to a total of 4gbs. Should I fill my second riser with 512? Or should I go with 2x1gbs?
     
  15. Macinposh macrumors 6502a

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    #15

    Depends..

    Are you gonna be satisfied with 4GB?
    If yes,then get the 4x512MB.

    Because FB-Dimms should be installed in matched pairs.

    If you know that you will crave more memory in the near future,dont buy them.

    Buy instead 2x1GB, or more preferably,suck it up and buy 2x2GB now.
    And take a performance hit (albeit small) untill you get a matching pair for them in the future.

    I agree,it is a bit shortsighted to buy the 512MB sticks and fill up your risers with them. When you update,they will be harder to get rid of than 1GB or 2Gb sticks.
     
  16. djhspawn macrumors member

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    #16

    2 x 1gb it is.. thanks.
     
  17. trainguy77 macrumors 68040

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    #17
    Your mistaken. 4x1 provides you with 256bit memory processing. 2x2 would only give you 128 bit memory processing.
     
  18. maberga29 thread starter macrumors member

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    #18
    Does anyone know what kind of difference 64 bit vs. 128 bit would make? (or 128 bit vs. 256). Anyone seen benchmark tests done on something like this?
     
  19. trainguy77 macrumors 68040

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    #19
  20. disconap macrumors 68000

    disconap

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    #20
    Is there one of those for the G5? I have mismatched RAM in mine and have always been curious if there was an optimum way to install it (I just went largest pair to smallest pair, so slot one is 2X1gb, slots 2 and 3 are 2X512, and slot 4 is 2X256)...
     
  21. CanadaRAM macrumors G5

    CanadaRAM

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    #21
    Nup. By definition, you don't have mismatched RAM in your PowerMac G5, it would not run without matched pairs - which is what you have. The G5 doesn't know from 256 bit access so there is no advantage to installing a matched 4-some, so matching between the different pairs is meaningless.
     
  22. irishgrizzly macrumors 65816

    irishgrizzly

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    #22
    Do we have any benchmarks showing optimum RAM placement Vs random placement? I'd like to know what people are getting worried about. I suspect it's only a couple of % difference. If theirs no benchmarks online maybe somebody here could reset there RAM and run a test? :)
     
  23. Sun Baked macrumors G5

    Sun Baked

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    #23
    The performance between dual and quad isn't as much as not having enough memory which can drastically cut performance.

    Stick in the most memory you can, in the fewest slots, so you don't have to ditch memory with your next upgrade as you move on your way to 32GB of RAM.
     
  24. CanadaRAM macrumors G5

    CanadaRAM

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    #24
    They're out there somewhere -- can't find them at the moment,

    But here is the rundown

    The sockets 1 and 2 on each riser are faster than the sockets 3 and 4 --- because in the FB-DIMM method all memory actions are sent first to the 1 and 2 sockets, and if the addresses are not present on those chips, they are then forwarded to the 3 and 4 sockets of that riser. This creates additional latency. So rule #1 is: Put your largest RAM DIMMs in the 1 and 2 sockets, because you want most memory activity to remain in the faster sockets.

    Rule #2 is that there is a small (according to Anandtech, 3%) gain to running a matched quad, that is, 256 bit access. So if you have 4 DIMMs of the same size, put them in the same sockets (Riser A 1 and 2, Riser B 1 and 2)

    But then there's Rule #3: Never buy smaller RAM DIMMs than you need to, just to make a quad. Adding 2 more 512s in order to make 4 x 512 would be foolish. Buy the largest RAM modules you can, as Multimedia said.

    (also, there is some suggestion that single rank modules, like the 512s, are slower than dual rank modules - most 1 and 2 Gb modules are dual rank. Ranks is a term used to describe the organization of the logical memory rows and columns on the physical chips on the module. This is by no means clear yet, and should not be a factor in your decision other than - don't buy 512's.)
     
  25. contoursvt macrumors 6502a

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    Jul 22, 2005
    #25
    4x1. If a stick fails, its no big deal...even running in pairs, you can pull one out and operate with 2x1 until the warranty item returns.

    If you have 2x2 and one fails, you might have a problem.
     

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