Confirmation of Westmere Memory Config

Discussion in 'Mac Pro' started by xgman, Aug 17, 2010.

  1. xgman macrumors 601

    xgman

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    #1
    eidt: the 6 core is on a workstation board it appears and not a server board. The server boards may or may not be dual channel capable but the 4 slot boards are 3 + 1, so disregard the rest of this post. Sorry about the misinfo. If only Apple had spelled this out for us. . . . .


    I spoke with the Micron engineer who personally tested the 4, 6 and 12 core 2010 mac pros on August 9th with regard to memory compatibility.
    After a long conversation and some additional research he confirmed that in fact the six core Westmere Mac Pro is a dual channel memory system (integrated in the chipset) and NOT a triple channel system like the 2009 Nehalem chipset Mac Pro systems were. Therefore the best way to populate the 4 slots is to populate them all with identical memory which will run in effect in dual channel mode.

    In addition. He stated that he in fact tested 8GB sticks of 1333 ram in the six core system and it did recognize and run the 8GB sticks. In fact Crucial has these 8GB sticks (albeit very expensive) listed now on their site as compatible with the 2010 Mac Pros.

    I certainly wish I had this info when I placed my memory order with Transintl. Nevertheless, it seems to indicate that the max amount of ram for the six core is looking much better indeed. By the way, the board is a derivative of the Intel 5520 for anyone who is interested.

    "Unlike Core i7, however, mainstream desktop/mobile Westmere chips will not feature a QPI bus or a triple-channel memory controller. Rather, we'll revert to a dual-channel controller and have no QPI clock to worry about"
     
  2. reel2reel macrumors 6502a

    reel2reel

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    #2
    Nice, thanks for posting this. We should get tests from diggloyd, too. :)
     
  3. xgman thread starter macrumors 601

    xgman

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    #3
    I forwarded this to him. he is going to test this as soon as a system arrives.
     
  4. skiffx macrumors 6502a

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    #4
    I just cancelled my order of 4x4 and replaced it with 3x4gb thinking it was triple, so this is 100% confirmed that it runs as dual channel and 4x4 would run faster?!
     
  5. xgman thread starter macrumors 601

    xgman

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    #5
    Yes. Everyone wrongly assumed it would be as the 2009. (well most everyone )
     
  6. lssmit02 macrumors 6502

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    #6
    I'm not sure this is right. According to Apple, the chip in the six core is the W3680. According to Intel's site,
    . Link. I assume this means it's triple channel memory. Note also, Intel's site also says the maximum amount of memory is 24GB.
     
  7. xgman thread starter macrumors 601

    xgman

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    #7

    Westmere is based on dual channel. Not sure what that is referring to above.

    Westmere’s memory controller can drive two DIMMs per channel at the full 1.33GT/s. Current Nehalem systems (and most AMD systems) run two DIMMs per channel at reduced bandwidth; Nehalem’s memory controller operates two DIMMs per channel at 1.06GT/s, sacrificing about 20% of the bandwidth.

    the Nehalem core supported three channels of DDR3 memory, but you could only acheive maximum speed (1333mhz) with a single DDR3 DIMM per channel. With Westmere, Intel has tweaked the memory controller for performance, so now you can still get to that 1333mhz number with two DIMMs installed per channel. An end user can now buy cheaper, lower density DIMMs without fear of performance degradation. The new and improved memory controller also supports new low-voltage DDR3 memory modules.
     
  8. Nautigar macrumors regular

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    #8
    Do you have a link or source to support this claim?

    I am rather sure this is wrong ...
     
  9. deconstruct60 macrumors 604

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    #9
    Err the Nehalem 2009 also is dual interleave mode if fill 4 slots. If these experiements were in filling 4 slots then this is no suprise, nor an confirmation that it solely runs in dual interleave mode in all contexts. ( Very unlikely that this interleave mode does not change as the configurations are changed. )



    The problem with 8GB DIMMs and that approach is that you end up with 32GB. The spec sheets on the 3680 say that it tops out at 24GB.

    http://ark.intel.com/Product.aspx?id=47917&processor=W3680&spec-codes=SLBV2
     
  10. xgman thread starter macrumors 601

    xgman

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    #10
    To be honest we need to know exactly which model Intel motherboard this is based on and is it in fact the W3680 or the X5680. The resulting answer is quite different. The W3680 is a workstation processor that fits on theWX58EP Intel board and does have triple channel 3 slots plus on extra slot.

    The X5680 fits on a server board, like the Intel 5520 and they use dual channel.

    So which is it?
     
  11. trankdart macrumors member

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    #11
    So the 2010 Nehalem-based quads use a different chipset? Different mobo? They're still Nehalems but they have fewer memory controllers than the Nehalems in the 2009 version? Or does the Westmere use two channels while the 2010 Nehalems still use 3?

    I would bet my house that the Micron engineer is mistaken. I believe Apple is using the same motherboard with the same or nearly the same chipset as last year, and that the Westmere has the 3 memory channels that Intel most unambiguously says it does, just like the Nehalem. I think the Westmere goes into the same socket on the same board with the same chipset as the Nehalems (it certainly does in my Linux server), and that all of them talk directly to the main memory subsystem with their 3 memory controllers independently of the chipset anyway.

    Unless there is a technical document from Apple or Intel confirming what the Micron employee said, I see no reason to believe it. It contradicts all the other available evidence.

    TD
     
  12. lssmit02 macrumors 6502

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    #12
    According to Apple it's the W3680 for the six core Mac Pro.
     
  13. Umbongo macrumors 601

    Umbongo

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    #13
    5520 is triple channel with two sockets each with their own memory.
     
  14. VirtualRain macrumors 603

    VirtualRain

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    #14
    Ok, that makes no sense at all. The Memory Controller for Nehalem/Westmere is on the CPU die, not on the chipset... so you've lost me here.

    Also, most certainly, the memory controller on Westmere is the same as on Nehalem... that is... a tri-channel controller.

    I suppose it might be possible, that the 2010 CPU daughter card is only using 128 bits of the 192 bit memory bus with two DIMM sockets wired to each of two 64 bit channels, but that would have required a completely unnecessary redesign of the CPU daughter card to provide down-graded performance. Very unlikely Apple did this.

    This is complete nonsense... where did this quote come from? EDIT: I see this came from the Techgage page which is in reference to Arrandale and Clarkdale.

    Of course all Nehalem/Westmere CPU's have a QPI bus to communicate with the X58 chipset.
     
  15. xgman thread starter macrumors 601

    xgman

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    #15
    Should have merged these threads:

    the W3680 is a workstation processor, not a server processor and would go into a Intel WX58EP motherboard. Now, I can't confirm that is the board the Apple is based on, but no server board is listed as compatible with the W3680. That means our original thoughts on the 3 channels are correct. I am going to test 8gb x 3 as soon as I can. Sorry for any confusion. Apple could have given us a memory config lesson on this but .. .
     
  16. deconstruct60 macrumors 604

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    #16
    Self contradictory statements. In the first there are only two. Later Westmere is Nehalem with an update so that can run two banks of DIMMs at the higher speed. The latter is true. The former... have no idea where it comes from.

    Running both bank 1 and 2 at 1333MHz doesn't necessarily make Westmere "dual channel". That would be one way of implementing it but likely kept the physical channel the same, just improvements on processing the signal quality. Each channel can support up to 3 DIMMs. Most designs conserve board space though and leave the 3rd off. (It additionally drops the memory transfer speed even more for both new and tweaked versions. )
     
  17. xgman thread starter macrumors 601

    xgman

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    #17
    There actually are dual channel memory based server boards and triple channel based workstation boards both taking different westmere processors and therein lies the confusion. Bottom line is Apple should have spelled all this out in detail. How else are we to decide how to configure the optimal size, number of sticks and speed of the ram? Anyway, sorry again for any confusion I may have caused.
     
  18. sirnh macrumors regular

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    Aug 16, 2006
    #18
    The memory controller is in the the processor package. I think a board vendor would have to go out of their way to limit a Westmere to just dual channel, mainly by providing just 2 slots. The controller will default to triple channel if 3 modules are installed, and dual channel if 2 or 4 modules are installed.
     
  19. xgman thread starter macrumors 601

    xgman

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    #19

    I think they are using a board like this:

    http://www.intel.com/products/workstation/motherboards/wx58bp/wx58bp-overview.htm
     
  20. trankdart macrumors member

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  21. glassbathroom macrumors 6502

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    #21
    Now I am really confused. I am guessing we are not going to finally resolve this 100% until someone has a new MP and has tested it. Is this correct?
     
  22. trankdart macrumors member

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    #22
    I agree there remain unanswered questions, and I don't think anybody here is going to do the test that resolves them. And I don't think a Kingston or Crucial employee who gets happier the more memory sticks get installed is a reliable source for answers (except maybe whether 8GB sticks work at all).

    There are some questions only Apple can answer. Intel can't even answer them. Example: on a DP machine, how does the Nehalem NUMA architecture play into the whole memory channel latency story? 2 channels, 3 channels or no channels, how much latency is added if one CPU has to go over the interprocessor QPI link to get data in the memory attached to the other one? That depends to some extent on how (and whether) the operating system deals with the tricky fact of NUMA.

    I think it's going to take anandtech or somebody like that to come up with some meaningful numbers. It would be nice if Intel would just answer, completely and in plain language, the simpler questions, like PRECISELY what happens when you populate that 4th slot?
     
  23. dhro1 macrumors newbie

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    Apr 20, 2010
    #23
    I fully agree with this. I enquired at crucial UK about the possibility of a compatible 3x4GB set for the six core and the response was:

    Thanks for your e-mail.

    This system can support up to 16GB over the four slots (4GB per slot) and the system uses Dual Channel functionality so we would recommend installing matching pairs.

    Please also bear in mind that a 32-bit Operating System will only see and utilise around 3GB when more is installed.

    You can order the compatible 4GB memory modules at the following link:

    http://www.crucial.com/uk/store/partspecs.aspx?imodule=CT51264BA1339

    Or you can order the 2GB memory modules here:

    http://www.crucial.com/uk/store/partspecs.aspx?imodule=CT25664BA1067

    Or you can order the 12GB kit 3x4GB modules here:

    http://www.crucial.com/uk/store/partspecs.aspx?IMODULE=CT3KIT51264BA1339

    Please let us know if we can offer additional assistance or advice.

    This directly contradicts their claim of a maximum of 32GB and the 8GB sticks they sell in pairs only on their compatibility page. While the memory they recommend is non-ECC and I'm sure OS X SL is predominantly 64 bit and has no problems addressing more than 3GB.
     
  24. xgman thread starter macrumors 601

    xgman

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    #24
    I spoke with a high level apple rep last night and they agreed that apple should have posted a full description. Of the memory channel setup for each version of the new Mac pro. They failed to understand the "pro" computer needs "pro" explanations critical to how buyers will configure their orders for optimal performance. Hopefully they will update the spec chart. Sorry for the bad info previously posted on this. It has been an eye opening lesson. Hopefully I will be able to test some 8gb modules on this next week, but there is no guaranty they will work.
     
  25. mattmower macrumors member

    mattmower

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    #25
    A small amount of extra information, I emailed Crucial in the UK about their 8GB part and whether they had tested on pre-release units and they responded:

    >Thanks for your email. I can confirm that the 2010 6 Core Mac Pro will
    >support 8GB per slot for a 32GB capacity. We have indeed tested the 8GB
    >modules to work on pre release units of this model and we guarantee them
    >to be compatible.

    Matt
     

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