How to maximally utilize 24GB mac pro memory??

Discussion in 'Mac Pro' started by silverlining101, Jul 21, 2011.

  1. silverlining101 macrumors newbie

    Jul 21, 2011
    Dear All,

    I would really appreciate your input on this matter -

    we bought a new 2X2.4Ghz dual quad core xeon processor mac pro - it came with 6 GBs memory but I did not realize that Apple sent 6*1 GB cards instead of 1*6 GB card. In any case, we bought 3*GB cards from an external vendor but realized that while these cards were compatible with the machine, they were not compatible with the other cards (ie. the machine would not start up when all were together). The machine has 8 memory slots in total so we just decided to remove the 6*1GB and replace with the 3*8GB cards (though, ideally, we would like as much memory in it as possible).

    We placed the 3*8 GB cards all on one side....I understand that some configurations better help the computer use all the memory. I am not sure if something is wrong with our current configuration but I am currently running some memory intense bioinformatics and my activity monitor says that only 3.66 GB memory being used, 7.65 inactive, 1.1 wired and 11.57 free. 100% of the processor is being used by this program.

    I am confused as to how to ensure that the 24GB memory is being maximally used as I believe my programs will run a lot faster if they were....

    any thoughts would be much appreciated!

    Thanks a lot!
  2. jonnymo5 macrumors 6502

    Jan 21, 2008
    First place to look is make sure the program you are using is compiled for 64-bit.
  3. silverlining101 thread starter macrumors newbie

    Jul 21, 2011
    It is, yes.

  4. iSee macrumors 68040


    Oct 25, 2004
    It's up to the program to use available RAM.

    You have ~19GB available (free + inactive), so no problem there.

    The program itself is not using the RAM.
  5. xgman macrumors 601


    Aug 6, 2007
    Some pro apps such as Photoshop and some DAW apps, etc., have preferences panels that allow you to set how much memory is allocated to them.
  6. silverlining101 thread starter macrumors newbie

    Jul 21, 2011
    Good call - I am using R - will look to see if I can change the amount of memory being used.

    So do none of you think the configuration of my memory slots (all 3*8GB cards on one side, one behind the other - I don't recall if they are on the A or B side but they are all together).
  7. hammten macrumors regular

    Jul 7, 2008
    CorRect me if im wrong but when you change the memory config. The mac pro pops up a box upon startup telling you if the memory is installed in the correct slots. At least that is what mine did....
  8. ytk macrumors regular

    Jul 8, 2010
    The position of the DIMMs won't make much, if any noticeable difference in performance, and certainly won't affect memory usage at all. If you want to be sure, you can run the Memory Slot Utility to see if your DIMMs are installed in the recommended slots. It starts automatically on bootup any time you change the RAM configuration, or you can run it manually from /System/Library/CoreServices/Memory Slot

    Regardless, 24GB is a LOT of memory, and you're unlikely to use that much on a daily basis. Actually, you'd be hard pressed to fill that up no matter what you do. I have 24GB in my 12-core Mac Pro, and even running Photoshop, Avid, Final Cut Pro, several compositing and 3D applications, Google Chrome, Safari, and miscellaneous other apps, all while rendering video in the background using Compressor, I've never managed to use all of my available RAM. Unless you're manipulating large databases or something using a 64-bit application, don't worry about it. Applications will request more RAM as they need it, so if you're not using up all the RAM you have installed, it's just because nothing you're running currently needs the memory.
  9. silverlining101 thread starter macrumors newbie

    Jul 21, 2011
    I am manipulating large datasets and my code has been running for well over 1.5 hours. I just wonder if the program pulled more memory if it would expedite the process.
  10. silverlining101 thread starter macrumors newbie

    Jul 21, 2011
    I have read that it does.....mine did not. But when I go to - About this mac - it recognizes that it has 24 GB.
  11. spidey3 macrumors regular

    Jul 1, 2010
    Have to agree here, and note that if you are seeing 100% CPU on all 8 cores, then there is really not much more you can do to speed things up. If you were memory bound in any way, then the machine would be paging, and you would not see 100% CPU usage.

  12. Zwhaler macrumors 604


    Jun 10, 2006
    Interestingly enough I have a Mac Pro 5,1 2x2.93 with 24GB RAM I can tell you that I achieved optimum memory bandwith using this configuration:

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

    I know this because when I installed the sticks the OS told me that was the best way to arrange them and it works GREAT !!!! In your case try this:

    Slot 1: 8GB
    Slot 2: 8GB
    Slot 5: 8GB
    or like you said fill slot 1, 2, and 3 with the sticks. See if the computer returns a message about how to best configure the 3 sticks

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