Using all slots in ram. -- 4,1 to 5,1 firmware update.

Discussion in 'Mac Pro' started by Korican100, Jun 20, 2014.

  1. Korican100 macrumors 6502a

    Korican100

    Joined:
    Oct 9, 2012
    #1
    So I am about to do the 4,1 to 5,1 upgrade w/ a w3690 3.46 hex.
    I know on my mac pro3,1, I was advised to fill all the slots for increased speeds.

    I heard that to use my new ram @ 1333hz, I would only be able to use slots 1-3. How much of a performance loss can i expect using only 3 slots? vs 4 slots @ 1066hz?



    I feel I maybe misinformed also. If the speed differences are completely negligible, please inform me.
     
  2. Studio K macrumors 6502

    Studio K

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    Feb 17, 2013
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    United States
    #2
    What's most important is that you have enough ram.
    If you can achieve that by using the 3 slots (for tri-channel @1333Mhz), then that would be ideal, I suppose.
    If you need to use the fourth slot to have enough ram, then I believe that the additional memory would outweigh the speed penalty.

    The consensus seems to be that the speed difference b/n 1066 and 1333 is nominal.
     
  3. MacVidCards Suspended

    Joined:
    Nov 17, 2008
    Location:
    Hollywood, CA
    #3
    Don't know where this 1066 speed comes from.

    You can use 4th slot at 1333 unless system profiler is lying. (It does sometimes)

    With a "W3xxx" processor you are limited to 3@16 GB and 1 @ 8 GB for Max of 56 GB.

    To get to 64, use a X5xxx CPU.

    Nobody has found a 32 GB module that works yet but I am still hopeful.
     
  4. Studio K macrumors 6502

    Studio K

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    #4
     
  5. Korican100 thread starter macrumors 6502a

    Korican100

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    Oct 9, 2012
    #5
    this is also what I read. That's why I wanted to know if 1333 w/ 3 slots is better than 1066 @ 4. Or does the "must fill up all slots for optimal speeds" rule apply to '09-'11 machines?
     
  6. reco2011 macrumors 6502a

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    May 25, 2014
    #6
    Aside from benchmarks and very high memory demand applications you won't be able to tell the difference. As Studio K said...if you memory demands can be met with three slots that's ideal. If not then load up all four. Either way you're unlikely to see a difference.
     
  7. MacVidCards Suspended

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    #7
    If someone knows of a specific test to find actual speed I will be happy to run on a X5650 upgraded single CPU.

    Runs 64GB of RAM.
     
  8. h9826790 macrumors 604

    h9826790

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    Apr 3, 2014
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    Hong Kong
    #8
    No, only use slot 1 2 3 is the optimum setting for Mac Pro 4,1 and 5,1.
     
  9. bxs macrumors 6502

    Joined:
    Oct 20, 2007
    #9
    Slots 1, 2 and 3 are best for each of the processor's 3 memory channels. If all slots are used then simultaneous access to some of the memory by the processors will have to share a memory channel. This in effect can slow down memory access at times.

    The budget may dictate 64GB so in this case 4x 8GB sticks for each processor would be done.

    If the budget can stand it, then use 96GB and place 3x 16GB in slots 1/2/3 for each processor.
     
  10. flowrider macrumors 601

    flowrider

    Joined:
    Nov 23, 2012
    #10
    For optimal performance use slots 1,2, & 3. The 35XX, 36XX, 55XX, @ 56XX Xeons have three memory channels. On a 4,1 and 5,1 Mac Pro, Slots 3 & 4 share the third channel. Therefore if you fill channel 1, 2, & 4 you won't see the RAM in the 4th slot. But, using the fourth slot along with the third probably won't be a big performance hit, but there will be some slowdown that you may not notice. However, my preference for my Dual CPU 5,1, I've left slots 4 and 8 MT.

    Lou
     
  11. brand macrumors 601

    brand

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    Oct 3, 2006
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    127.0.0.1
    #11
    There is no 2011 Mac Pro. The 2009 model is identified as 4,1 while the 2010 and 2012 models are both identified as 5,1. The 4,1 is technically different than the 5,1.
     
  12. 666sheep macrumors 68040

    666sheep

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    Poland
    #13
    Quad ranked registered 1333 RAM shows itself in ASP as 1066 when all 4 slots are occupied.
     
  13. MacVidCards Suspended

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    #14
    For the sake of clarity, which RAM is showing up as 1333 with all 4 slots populated?
     
  14. bxs macrumors 6502

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    Oct 20, 2007
    #15
    I have the OWC's 64GB (8x 8GB sticks) for my 5,1 and it ALL runs as 1333 MHz using X5670 processors.
     
  15. 666sheep macrumors 68040

    666sheep

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    #16
    2R (dual rank) ones for sure. Unbuffered and registered.

    OWC 8GB ones are 2R according to OWC website.
     
  16. fredr500 macrumors regular

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    Apr 12, 2007
    #17
    Just to be clear

    I have a quad 2.8 5,1. It came with 3GB (WTF?) so I ordered 16GB (2x8GB) from OWC, it arrives today.

    I was planning on the 2 new 8's in front, 2 of the old 1GBs in back.

    I assume it is better to have the extra gig at a reduced speed than just use one of the old sticks. It's better to have slightly slower 2GB than a faster 1GB when I need the extra space, correct?
     
  17. flowrider macrumors 601

    flowrider

    Joined:
    Nov 23, 2012
    #18
    ^^^^Since you only ordered Two DIMMs you won't get the benefit of 3 channel memory any way, so yes your plan is OK.

    Lou
     

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  18. fredr500 macrumors regular

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    Apr 12, 2007
    #19
    I didn't realize that when I ordered the 2 DIMMs. Bummer.

    How much real-world difference would I see with 3 matching DIMMs? Besides the increase from 16 to 24GB.
     
  19. reco2011 macrumors 6502a

    Joined:
    May 25, 2014
    #20
    Probably none.
     

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