Since triple channel memory, why aren't slots in multiple of 3s??

Discussion in 'Mac Pro' started by Luba, Dec 13, 2011.

  1. Luba macrumors 6502a

    Luba

    Joined:
    Apr 22, 2009
    #1
    Since the MP uses triple channels to access memory, why aren't the memory slots in multiples of 3s, e.g. 6 slots and 12 slots, instead of 4 slots and 8 slots?

    For that matter, why did Apple limit the number slots in the Quad Core MP, couldn't Apple given the Quad Core more memory slots than 4??

    Finally, would you upgrade to 32GB (8GB sticks x 4) or 24GB (8GB sticks x 3). I believe installing sticks in multiples of 3 would give me a speed boost of about 5%, but if I ever needed or could use more than 24GB, then the extra memory would more than compensate the small 5% speed advantage?

    Thanks . . . btw, I video edit and do a little Lightroom 3 and Photoshop. At this point I am not sure what to use to video edit. Since I am a student I can get Avid Media Composer 6 at a bargain price or I could buy Final Cut Pro X or learn to use Premiere 5.0 which I already have.
     
  2. philipma1957 macrumors 603

    philipma1957

    Joined:
    Apr 13, 2010
    Location:
    Howell, New Jersey
    #2
    this is why there are 4 slots. as for why 4 slots and not more. the cpu can handle 48gb ram. so more slots would make passing 48gb ram too easy. btw the best you can do is buy 3 16gb sticks of ram... gives you max ram 48 and triple channel.




    https://www.superbiiz.com/detail.php?name=D3-10R16GS


    if you have a quad core 2010 3 of these is the max option
     
  3. wonderspark, Dec 13, 2011
    Last edited: Dec 13, 2011

    wonderspark macrumors 68030

    wonderspark

    Joined:
    Feb 4, 2010
    Location:
    Oregon
    #3
    I edit video, and I use four sticks. I had 4x4GB and recently switched to 4x8GB. It makes a big difference. More RAM is far more valuable than triple channel, if you ask me. It's still double channel, and 1333MHz RAM is fast so unless you can afford 3x16GB, I'd do 4x8GB.
     
  4. cherry su macrumors 65816

    cherry su

    Joined:
    Feb 28, 2008
    #4
    The daughterboard is too small for 12 slots with the two giant heatsinks. I suppose Apple went with 8 to not make the new Pro seem like a downgrade compared to previous generations, which had 8 slots.

    Same reasoning above, except SP Pros have an even bigger heatsink.
     
  5. JesterJJZ macrumors 68020

    JesterJJZ

    Joined:
    Jul 21, 2004
    #5
    I've been thinking about this recently as well. Trichannel vs. more memory. RAM is relatively cheap these days. What would be better, 4GB x 6 (24GB) or 4GB times 8 (32GB)?
     
  6. Umbongo macrumors 601

    Umbongo

    Joined:
    Sep 14, 2006
    Location:
    England
    #6
    This is likely the correct answer, with the single processor model probably having only 4 to further distinguish the difference between the two models. The should have had 9 memory slots on the dual processor model, but real world performance differences were likely considered too small to bother or something.

    Whatever you can afford.
     
  7. JesterJJZ macrumors 68020

    JesterJJZ

    Joined:
    Jul 21, 2004
    #7
    Well it's only $50 more for 32GB. Price aside, what is better, a little more memory or staying trichannel?
     
  8. wonderspark macrumors 68030

    wonderspark

    Joined:
    Feb 4, 2010
    Location:
    Oregon
    #8
    Heck, I'll bite. I have 32GB now, and my geekbench is currently 15646.
    I'll pull a stick and see what I get in triple channel mode. Standby...
     
  9. wonderspark macrumors 68030

    wonderspark

    Joined:
    Feb 4, 2010
    Location:
    Oregon
    #9
    Ok, ready for the results? 24GB installed (3x8GB sticks). Best of three runs was:
    15693, first run.
    Second was 15639, third was 15633.

    When I did the tests before with 32GB, the fastest was the second of three runs, as a note of interest.

    So, I gained at best 47 points. Averaging it out, it's almost the same. It doesn't really sell me on the whole triple channel benefit. In fact, it reaffirms my belief that 32GB in double channel is far more useful than 24GB in triple channel.

    ----------

    For fun, I'm going to reboot in 32-bit mode (since 5,1 firmware boots in 64-bit) and re-run the test. Then, I'll reinsert my fourth stick, boot in 32-bit, and run it again. We'll have data for 24GB vs 32GB in both 32 and 64-bit kernels. :)
     
  10. Inconsequential macrumors 68000

    Joined:
    Sep 12, 2007
    #10
    Im interested in 1066MHz and 3 sticks and 1333Mhz with 4 sticks.

    Thinking that I'll upgrade my MP4,1 to a 5,1 with a W3680, 16GB 1333MHz and a 5770/5870 instead of a MP6,1.
     
  11. wonderspark macrumors 68030

    wonderspark

    Joined:
    Feb 4, 2010
    Location:
    Oregon
    #11
    I ran Geekbench on my 3.33GHz Quad (W3580) with 16GB of 1066 RAM and got 10432. That was sometime in 2010.
    After upgrading to 5,1 firmware and putting in 32GB of 1333 RAM, I scored 11627 on that same CPU.

    Since then, I swapped in a 3.33GHz Hex (W3680) and ran both the 32GB and 24GB of 1333 RAM. I also booted in both 32 and 64-bit kernels. The results:

    32GB in 64-bit kernel (four runs)
    15631
    15589
    15658
    15619

    32GB in 32-bit kernel
    15598
    15567
    15606
    15608

    24GB in 64-bit kernel
    15693
    15639
    15633
    15695

    24GB in 32-bit kernel
    15616
    15618
    15706
    15663

    (fastest in bold)

    So, I found it interesting that the fastest of all of them was 24GB in 32-bit kernel. Of course, the numbers fall all over the place (within a range) so it's hard to say how accurate the test is. Still, 24GB of RAM had higher numbers by 48 points at best.
     
  12. wallysb01 macrumors 65816

    Joined:
    Jun 30, 2011
    #12
    Looking at the board, I think they actually have plenty of space for 12, 6 per CPU. Those ram slots are fairly spread out compared to other boards. Being in a field that will use all the RAM you have (and I mean all the way up to 1 TB of RAM), the 2010 model supporting 192 GB of RAM sure would be nice. But 96 is pretty good.

    I'm hoping that with quad channel memory being supported on SB-E, Apple shoves an extra couple slots in there for the 2011. Or hopefully the board can support 256 GB of RAM, since it probably won't be too long until 32 GB sticks become kinda reasonable (I'm thinking maybe end of next year?). So if they do keep only 8 slots on the DP, then at least it could be 8x32.
     
  13. philipma1957 macrumors 603

    philipma1957

    Joined:
    Apr 13, 2010
    Location:
    Howell, New Jersey
    #13
    an eight core sp cpu with 4 x 32gb would be nice. wait for the new ones to come out.. I hope to buy one and do a long thread on a cpu upgrade like I did with the 2010.
     
  14. dknightd macrumors 6502

    Joined:
    Mar 7, 2004
    #14
    The reality is there is more to life than geekbench. Sometimes 3 memory cards might provide a slight increase in real life speed. Sometimes 4 memory cards might be better (especially if you need more memory.) I have no idea why they provided 4 slots per cpu - perhaps because it is sometimes better than 3? I'd buy enough memory in 3 slots so you do not have to swap - if you need more memory later, add a 4th stick.
     
  15. MacsRgr8 macrumors 604

    MacsRgr8

    Joined:
    Sep 8, 2002
    Location:
    The Netherlands
    #15
    Tnx for testing and posting!!
     
  16. wallysb01, Dec 14, 2011
    Last edited: Dec 14, 2011

    wallysb01 macrumors 65816

    Joined:
    Jun 30, 2011
    #16
    Given the extreme mark ups for Apple CPU upgrades that sure makes sense. If this DP 2.4 was actually mine, I'd sure like to see what a couple of those X5670 would do.

    It will be interesting to see what happens in a couple months and how all the final specs shack out.
     
  17. wonderspark macrumors 68030

    wonderspark

    Joined:
    Feb 4, 2010
    Location:
    Oregon
    #17
    I agree that Geekbench isn't the best way to measure reality, but I thought it would be worthwhile. I got a huge jump in actual performance by jumping from 16GB 1066 to 32GB 1333 for use in After Effects and Premiere Pro CS5. I got another jump when I swapped in a 6-core, but that was more because I *could* than actual need. :p It did take care of my Hex-envy.
     
  18. derbothaus macrumors 601

    derbothaus

    Joined:
    Jul 17, 2010
    #18
    If reality was measured the triple channel set would hold zero benefit. Only super cool in tests. Never seen it make a dent in anything like Photoshop or After Effects.
     
  19. wonderspark macrumors 68030

    wonderspark

    Joined:
    Feb 4, 2010
    Location:
    Oregon
    #19
    Speaking of Photoshop... I have a neat little script that creates a RAMdisk that I sometimes run prior to opening Photoshop. I set it as my scratch disk, and wow! Everything is *ahem* snappy! :)
     
  20. Allmec macrumors newbie

    Joined:
    Feb 13, 2007
    #20
    MacPro and Memory Grrrrr

    MacPro 4.1 have 4x4GB and 4x2GB and am REALLY struggling to get it to recognise all 24GB.. best I can get is 18GB

    Memory Utility says...annoying conflicting results.
    It's current favoured option is to
    Slot 1: 4GB DIMM Slot 5: 2GB DIMM
    Slot 2: 4GB DIMM Slot 6: 2GB DIMM
    Slot 3: 4GB DIMM Slot 7: 2GB DIMM
    Slot 4: - Slot 8: -

    So what I am supposed to do with the extra 6GB ;(

    Any help?
     
  21. flatfoot macrumors 65816

    Joined:
    Aug 11, 2009
    #22
    This is what would make most sense in my eyes:

    Slot 1: 4GB DIMM Slot 5: 4GB DIMM
    Slot 2: 4GB DIMM Slot 6: 4GB DIMM
    Slot 3: 2GB DIMM Slot 7: 2GB DIMM
    Slot 4: 2GB DIMM Slot 8: 2GB DIMM

    Numbering taken from this Knowledge Base article.

    Please report back whether that did the trick.

    If it doesn't work, you might find a solution in the KB article.
     
  22. mamasboy macrumors member

    Joined:
    Jan 11, 2008
    #23
    Wonderspark wrote,
    "Ok, ready for the results? 24GB installed (3x8GB sticks). Best of three runs was: 15693, first run.
    Second was 15639, third was 15633.

    When I did the tests before with 32GB, the fastest was the second of three runs, as a note of interest.

    So, I gained at best 47 points. Averaging it out, it's almost the same. It doesn't really sell me on the whole triple channel benefit. In fact, it reaffirms my belief that 32GB in double channel is far more useful than 24GB in triple channel."

    ----------

    Wonderspark,
    I "wonder" if you'd mind sparing the time performing the 24gb vs 32gb (3dimms vs 4dimms) in the new OS 10.8.2? ...assuming you upgraded to ML.

    I'm curious to see if the truly 64bit OS in a truly 64bit machine (5,1) will use the memory differently these days...

    Thanks in advance,
    Lonnie
     
  23. wonderspark macrumors 68030

    wonderspark

    Joined:
    Feb 4, 2010
    Location:
    Oregon
    #24
    I haven't updated beyond 10.6.8, so I can't help you there. I may move to Mountain Lion one day... or whatever comes after ML. Right now, everything is perfect and awesome with Snow Leopard.

    I have ML on a 2012 Mac Pro, which I did my best to reconfigure so it acts like SL, haha.
     
  24. mamasboy macrumors member

    Joined:
    Jan 11, 2008
    #25
    Thanks for getting back Wonderspark!

    However, in the meantime Rob-ART of Barefeats confirmed via email that although the triple channel configuration is faster (although by not much) than the 4 dimm configuration - with my priorities of "CS6 performance" - I have more to gain with more RAM. In other words- fill the 4 dimms...

    Thanks,
    Lonnie
     

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