Best slots for 2x1GB + 2x4GB DIMMs?

Discussion in 'Mac Pro' started by kirkbross, Apr 12, 2013.

  1. kirkbross macrumors 6502a

    kirkbross

    Joined:
    Mar 6, 2007
    Location:
    Los Angeles
    #1
    What is the best DIMM configuration for 2 x 1GB sticks plus 2 x 4GB sticks, totalling 10GB.

    I have a MP 2009 (4,1) 4 core with four slots and can't seem to find out which slots are which channels and whether to go 1, 1, 4, 4 or 1, 4, 1, 4.
     
  2. Umbongo macrumors 601

    Umbongo

    Joined:
    Sep 14, 2006
    Location:
    England
    #2
    Slot 1 - 4GB - Channel 1-Bank 0 and interleaves with slot 2.
    Slot 2 - 1GB - Channel 2-Bank 0.
    Slot 3 - 4GB - Channel 3-Bank 0 and interleaves with slot 4.
    Slot 4 - 1GB - Channel 1-Bank 1.
     
  3. kirkbross thread starter macrumors 6502a

    kirkbross

    Joined:
    Mar 6, 2007
    Location:
    Los Angeles
    #3
    Cool... I thought there were only 2 channels... or more aptly, I don't comprehend memory channel architecture. :)
     
  4. ActionableMango macrumors 604

    ActionableMango

    Joined:
    Sep 21, 2010
    #4
    Maybe a dumb question, but if slot 1 and 2 are interleaving, and slot 3 and 4 are interleaving, shouldn't it be this:

    Slot 1 - 4GB
    Slot 2 - 4GB
    Slot 3 - 1GB
    Slot 4 - 1GB

    From Apple:
    [​IMG]
     
  5. Umbongo macrumors 601

    Umbongo

    Joined:
    Sep 14, 2006
    Location:
    England
    #5
    No, because you want balanced memory for optimal performance. So with this amount of memory you'd put 5GB on each of the two interleaving sets. You could probably use any placement combination and get the same level of real world performance to be honest.
     
  6. kirkbross thread starter macrumors 6502a

    kirkbross

    Joined:
    Mar 6, 2007
    Location:
    Los Angeles
    #6
    I tried both ways and matched pairs was the way to go. When I staggered them 1, 4, 1, 4 it only recognized 5GB RAM total. I have it like you have it above and it recognizes all 10GB.
     
  7. ActionableMango macrumors 604

    ActionableMango

    Joined:
    Sep 21, 2010
    #7
    I hesitate to give advice because I don't know what I'm talking about, but I have always read that when interleaving memory they should be matched pairs.

    Granted, in a typical PC the DIMM slots are laid out such that you need to alternate the sticks in order to interleave matched pairs. In a PC I would definitely do 4,1,4,1.

    But in the MP the slots must be laid out differently. The table I provided above from Apple shows the two-DIMM layout with both DIMMs placed adjacent to each other, not in alternating slots like you would in a PC.

    In any case, I also have 10GB of RAM and mine are installed 4,4,1,1. Whether this is ideal or not, I don't know. I do know that all 10GB are recognized and working.

    P.S. Your signature is out of date. :)
     
  8. Umbongo macrumors 601

    Umbongo

    Joined:
    Sep 14, 2006
    Location:
    England
    #8
    As long as it works is all that matters, as I said the staggered approach wouldn't give you significant performance differences anyway. I guess the Mac Pro has issues with the placement I suggested where other LGA 1366 boards don't.
     
  9. Tesselator macrumors 601

    Tesselator

    Joined:
    Jan 9, 2008
    Location:
    Japan
    #9
    Exactly right!
     
  10. kirkbross thread starter macrumors 6502a

    kirkbross

    Joined:
    Mar 6, 2007
    Location:
    Los Angeles
    #10
    Actually my sig is my home MP... the MP with 10GB is at work... it's a 2009 (4,1) MP.
     

Share This Page