10GB slower than 8GB in 2008 Mac Pro?

Discussion in 'Mac Pro' started by Delirium39, Jul 6, 2009.

  1. Delirium39 macrumors regular

    Joined:
    May 19, 2008
    #1
    Hello, I just received my package of matched memory (2GB x 4), to replace the measly 1GB x 2 that came with my 2008 mac pro. I know there's a performance increase when using 4 modules. If I also keep the 1GB x 2 in the system, for a total of 10GB, will I lose the speed increase, or is it enabled when you have at least 4 modules, and anything more than that comes along for the ride? Thanks for any info!
     
  2. southerndoc macrumors 6502a

    southerndoc

    Joined:
    May 15, 2006
    Location:
    USA
    #2
    It's my understanding that things work best if all the memory matches. So I think by adding in the 1GBx2 you will likely lose some performance. How noticeable that will be is a different question.
     
  3. Heb1228 macrumors 68020

    Heb1228

    Joined:
    Feb 3, 2004
    Location:
    Virginia Beach, VA
    #3
    I thought dual-channel just needed to be installed in pairs... not every stick in the whole system had to match.
     
  4. Delirium39 thread starter macrumors regular

    Joined:
    May 19, 2008
    #4
    Hmmmmm, well according to this article, the 8GB configuration would give me 6.5GB/s, while the 10GB configuration would give me 6.8GB/s. If true, I'm wondering what slot order gets that result. Accordng to OWC, I should be installing new memory in this order:

    Top Riser:
    1GB (stock)
    1GB (stock)
    2GB (matched new)
    2GB (matched new)

    Bottom Riser:
    2GB (matched new)
    2GB (matched new)

    Anyone know if this is correct?

    Edit: I think I found the answer here: http://eshop.macsales.com/Reviews/Framework.cfm?page=/Benchmarks/macproearly08ram/article.html

    Looks like running 10GB in the above configuration is the same or faster than the 8GB option.

    Thanks for all your opinions everyone!
     
  5. southerndoc macrumors 6502a

    southerndoc

    Joined:
    May 15, 2006
    Location:
    USA
    #5
    Maybe that's all you need.
     
  6. MegaMillions macrumors regular

    Joined:
    Feb 1, 2009
    #6
    I'm confused now about how this works. I didn't know you could have ONE chip in the upper riser, and ONE chip in the lower riser. I thought they had to be matched pairs.

    I had 4x512mb when I got my Mac Pro (two on the top riser, slots 1 and 2, and two on the bottom riser, slots 1 and 2).

    When I installed the two 2GB chips I just got, I put them in slots 3 and 4 of riser A. Is that correct? What's the order of how to put them in?
     
  7. åidån Guest

    Joined:
    Location:
    New Zealand
    #7
    How about putting one of your 1gb sticks from the top riser into the bottom, that would match everything up, wouldn't it.
     
  8. TheStrudel macrumors 65816

    TheStrudel

    Joined:
    Jan 5, 2008
    #8
    He's using the configuration specified by . I think the way the risers work means splitting it in that way would hurt, not help.
     
  9. Tesselator macrumors 601

    Tesselator

    Joined:
    Jan 9, 2008
    Location:
    Japan
    #9
    That's right. With the proper installation:

    [​IMG]
    You'll get dual channel from the 1st four 2GB modules and single channel access from the last 1GB modules. Buying two more 1GB modules will provide dual channel access to all modules.
     
  10. surflordca macrumors 6502a

    surflordca

    Joined:
    Nov 16, 2007
    Location:
    Ontario, Canada
  11. TheStrudel macrumors 65816

    TheStrudel

    Joined:
    Jan 5, 2008
    #11
    I think the general behavior of software makes any loss of speed negligible, and not worth worrying about until one is striping Intel X-25M SSDs to eliminate the storage bottleneck.
     
  12. Tesselator macrumors 601

    Tesselator

    Joined:
    Jan 9, 2008
    Location:
    Japan
    #12
    I think that indeed will make it more relevant. It's still relevant even now IMO though. Just not as much. :)
     
  13. mattlong1978 macrumors member

    mattlong1978

    Joined:
    Dec 4, 2008
    Location:
    United Kingdom
    #13
    Agreed I run 10GB with 2x4GB and 2x1GB and I've never felt it crippled my Mac in anyway regarding performance, infact a year down the line and it's still the most rapid system I've ever used
     

Share This Page