CS5 Ps & Pr, LR3 - double or triple channel memory benefits

Discussion in 'Mac Pro' started by Avery1, Sep 21, 2010.

  1. Avery1 macrumors regular

    Mar 14, 2010
    Can anyone speak from actual knowledge as to if CS5 Premiere Pro, CS5 Photoshop, and Lightroom 3 will actually make use of a triple-channel memory configuration (i.e. *real world* results are > 10% performance gain over double-channel)?

    I have an early 2009 8-core Mac Pro, and currently have 4x2GB RAM.

    I definitely want to upgrade the RAM, as running just LR + PS tanks the memory. Admittedly, I'm still not fully sure if I should be considering inactive RAM to be available... though, it seems to page out if free memory is 0 and inactive is sizable... so I think no.

    Anyhow, my upgrade options are:
    1) upgrade to 12GB (triple-channel) - $100
    2) upgrade to 16GB (double-channel) - $200
    3) upgrade to 24GB (triple-channel) - $850.

    3) would be ideal, but that's a pretty big jump in cost. If it will make some significant real-world differences in editing video and photos (versus option 2), I'd consider it -- though a bit reluctant.

    If anyone else is using CS5 Premiere Pro to edit HD with the standard video card, I'd be interested in hearing how much memory you see CS5 consume (I'm new to video and Pr).

  2. goMac macrumors 603

    Apr 15, 2004
    Double or triple memory channels will give you across the board performance boosts. How much is usually a matter of debate. But all the applications you list are pretty RAM heavy.
  3. Avery1 thread starter macrumors regular

    Mar 14, 2010
    Yeah, how much is the question.

    There are some interesting tests here -- where they did a double channel mixed-memory (2x(4+2)) configuration versus a triple channel. There wasn't a huge difference on the Premiere Pro, and even sometimes slower. However, they were on CS4, not CS5. With CS5 being 64-bit, I'm not sure if it would take more advantage of triple-channel -- or if 64-bit would have no effect (i.e. channel is not a bottleneck).

  4. Honumaui macrumors 6502a

    Apr 18, 2008
  5. Honumaui macrumors 6502a

    Apr 18, 2008
    fun info to read ;) I know I have 3 channel in my new one ? as 8GB sticks that way if I want or need the 32 GB mem I can jump up cause I would rather have a touch slower and the memory than not have enough ? also it seems to me where the speed really comes in is when you are taxing the system and that in reality is less often ? as many times its just retouching or other things then a few short shots of applying actions or things
  6. Avery1 thread starter macrumors regular

    Mar 14, 2010
    Yep, good stuff on that site. I'd previously read the articles he'd written about the 2009 MP performance -- a good read.

    I think the responsible thing to do is to buy the 4GB upgrade for $100 and see how it goes. If I'm still maxing out at 12GB, I can cross the 16GB/24GB bridge at that time.

  7. Avery1 thread starter macrumors regular

    Mar 14, 2010
    Thanks -- very useful!

    Definitely shows the performance increase going from 12-16 as small (< 10%) with PS CS5, versus pretty significant when jumping to 24GB. This seems to indicate the double/triple channel gains by CS5, further supported by the fact that on the macperformanceguide optimizing CS5 site -- seems to indicate CS5 PS memory usage for a large txn ~14GB.
  8. WardC macrumors 68030


    Oct 17, 2007
    Fort Worth, TX
    The maximum performance you are going to have on a single processor 2009 or 2010 Mac Pro is with 24GB of RAM (2x 8GB) and with the dual processor model 48GB of RAM (6x8GB). Installed in 3 slots most distant from the heatsink. This will allow for full triple channel DDR3 memory acceleration..

    One thing I noticed. When I had all 4 slots full on my Mac Pro, in Activity Monitor, it showed most of my RAM as GREEN "Free" space.

    When I have 12GB installed and only use 3 slots instead of 4, it displays most of my RAM in Activity Monitor as BLUE "inactive" space.

    The graph looks totally different when using 12GB vs 16GB. It's Blue instead of Green. From what I understand, when you have all 4 (*or 8 on duals) slots filled, it shares the memory bandwidth between chips 3 and 4 and your memory only runs at half of the speed that it would if you were using 3 slots.

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