Memory speed recognition on Mac Pro 5.1

Discussion in 'Mac Pro' started by fiberman, May 30, 2016.

  1. fiberman macrumors newbie

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    Mar 31, 2013
    #1
    Hi everyone! I've a Mac Pro 5.1 which I plan to upgrade soon. I plan to upgrade the CPU to a W3690 and install 64 Gigs of ram. So my question is: Can I upgrade to 1600MHz or 1866MHz memory? I have access to either from a friend. I think my system will only work at 1333MHz, which is ok, but since the upgrade is a great deal, will either work ok?
     
  2. h9826790 macrumors 604

    h9826790

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    Hong Kong
    #2
    NO, W3690 do NOT support 64G RAM. You need X5690 to run 64G RAM.

    YES, you can use 1600 / 1866 RAM. HOWEVER, no matter which CPU you use, max operating RAM speed is 1333MHz CL9. So, the higher speed RAM won't give you any benefit. Unless they are cheaper, or you may use them on other system. There is no reason to spend more money and buy the faster RAM.
     
  3. Synchro3, May 31, 2016
    Last edited: Jun 1, 2016

    Synchro3 macrumors 65816

    Synchro3

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    Jan 12, 2014
    #3
    You can use 3 * 16 GB + 1 * 8 GB RAM with a W3690.

    However I would prefer 3 * 16 GB because of triple channel.
     
  4. fiberman thread starter macrumors newbie

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    Mar 31, 2013
    #4
    Hmmm. I don't doubt you, but why do sites like "Mac Ram Direct" say you can max out a single hex core "Westmere" at 64Gigs? I'm curious. And yes, actually, I can't find the memory at a lower price anywhere else. I even thought of getting the 1866 and maybe use it later if I can get a good deal on a used 2013. Lol.
    --- Post Merged, May 31, 2016 ---
    Thanks Synchro3. So is the triple channel a characteristic of the CPU? Does the X5690 accommodate more bandwidth for memory? Having the extra RAM is nice, but if the CPU(X5690) can't utilize it efficiently, then I don't want to spend money un-necessarily. My dilemma is that I get a much better price if I purchase the four 16Gig sticks of either speed at once, rather than one at a time.
     
  5. DPUser macrumors 6502a

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    Jan 17, 2012
    #5
    My research confirms W3690 max RAM is 56gb and that both CPUs (W3690 and X5690) are triple channel. But, if you will actually use all the RAM, you are still better off with more in quad config.
     
  6. h9826790 macrumors 604

    h9826790

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    #6
    Because you can install a X5690 on a single processor 5,1. That's still Westmere, still Hex cores. They are entirely correct, but just didn't clearly state that a X56xx is a requirement.
     
  7. carylee2002 macrumors member

    carylee2002

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    Jul 27, 2008
    #7
    I have 48gb triple channel in my rig and that is plenty enough to run my adobe programs and pro tools. So you really don't need to up more than that unless you are using engineering programs.
     
  8. fiberman thread starter macrumors newbie

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    Mar 31, 2013
    #8
    Thanks h9826790. I researched the Intel website and compared the two chips. They are identical except for the fact that the x5690's maximum memory size is 288GB and the w3690's is 24GB, and of course the number of QPI links. So I'm wondering if that's maximum memory per channel or total memory the chip will use efficiently or recognize. Just for the sake of acquiring the knowledge I'd like to find out how all that is determined. If anybody can point me in the right direction I'd appreciate it. As far as what I'll end up purchasing, I'm still not sure. If I go with the 48GB and the 3690 I think I might be able to afford a SSD drive to boot, but having the extra RAM with the 5690 sounds good too. Thanks all for your insight and wisdom.
    --- Post Merged, Jun 5, 2016 ---
    Hello DPUser. What do you mean by quad config? Stay with the original quad core chip and just increase the memory? The quad chip will only see a maximum of 1066MHz RAM speed though right?
     
  9. h9826790, Jun 5, 2016
    Last edited: Jun 6, 2016

    h9826790 macrumors 604

    h9826790

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    #9
    You can treat that 24G as "max demonstrated memory size" from Intel.

    My personal guess would be the biggest stick was 8G by that time, so, 3 channel x8G is 24G. And that's been tested by Intel.

    And now, 16G stick is avail, therefore 48G is possible. However, Intel never update the spec since the CPU was released. Therefore, the spec in their webpage is not really up to date.

    Also, the max memory per channel still an unknown at this moment. However, on the cMP, it's been demonstrated that 3x16 + 8 is bootable and all memory ops normal. So, the max RAM size for W3690 is 56G at this moment.

    On the other hand, the max memory on X5690 is 288G (8G x12 = 96G per channel), I don't know if it's possible to run 576G RAM by a single X5690 (or even more). But due to max stick size is 16G at this moment. A single X5690 can drive 64G RAM on a cMP.

    Anyway, I guess what he mean "Quad config" is use all 4 slots for memory, but not staying with Quad core CPU.

    Also, apart from that 2 differences, the max temperature of W3690 and X5690 are also difference.

    If you still has no SSD yet. I think it's better to get at least a 120G SSD as boot drive, which can cost as low as $30. Rather than spend all the money on CPU + memory. Unless your workflow is very storage speed independent (e.g. some long time calculation which only depends on RAM size and CPU speed).

    For your info, if your workflow is not extremely special, and very different from other user. 48G RAM generally is more than enough. Despite that I have 48G of RAM, my Mac usually utilise around 30G most of the time (used + cache). The rest 18G can be fully utilise as cache when I encoding videos. However, the used part seldom go over 24G. So, the difference between 56G and 64G may means you have 32G cache or 40G cache. Of course 40G cache is better, however, it's hard to tell how much benefit you can gain from that extra 8G.

    I recently upgrade my RAM form 32G to 48G. From quad config back to triple config, from 1066 upgrade to 1333. However, without benchmark, I can't tell the difference. All I know is no matter how I stress my Mac, I never need the Swap now. Of course, if your workflow require sometime like running few virtual machines at the same time. Then 64G is the way to go.
     
  10. ZombiePhysicist macrumors 6502

    ZombiePhysicist

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    May 22, 2014
    #10
    It is possible to run 128GB at 1333mhz on the 3.46ghz part. I'm running that currently.
     
  11. DPUser macrumors 6502a

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    Jan 17, 2012
    #11
    Hello DPUser. What do you mean by quad config? Stay with the original quad core chip and just increase the memory? The quad chip will only see a maximum of 1066MHz RAM speed though right?
    I wasn't talking CPU, I was talking RAM. If your applications can use the extra RAM, that will more than offset the slight penalty imposed by going from three to four channels of RAM. Get the new CPU.
     
  12. h9826790 macrumors 604

    h9826790

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    #12
    OP was talking about a single CPU 5,1. So, cannot run 128G RAM at this moment.
     
  13. ITguy2016 Suspended

    Joined:
    May 25, 2016
    #13
    He' referring to a triple versus quad configuration of the memory. Since this generation of processors have three memory controllers optimal memory speed is achieve when memory modules are installed in sets of three. Using four memory modules breaks the optimal memory speed but allows for larger memory size.

    His comment went on to say if you're going to use all of the memory the sub optimal configuration (i.e. four [quad in this words] memory modules) provides then go with the sub optimal configuration. The larger memory size more than offsets the slight decrease in performance that results from such a configuration (if you will actually be using the additional memory available as a result of the fourth module).

    In all instances he is not referring to the processor.

    EDIT: Hmmm...looks like quoting errors had me responding to the wrong person. Anyway to delete this?
     

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