Can adding more memory slow down my Mac Pro?

Discussion in 'Mac Pro' started by Lumpydog, Jan 23, 2008.

  1. Lumpydog macrumors 6502

    Joined:
    Aug 3, 2007
    #1
    All:

    I just read this article: http://www.barefeats.com/harper3.html

    From reading it, my interpretation is that I may have actually slowed down my new mac pro by adding memory...

    I purchased an additional 4GB of Ram from OWC - Two x 2GB sticks. I placed the two new sticks in the top riser (4GB) and I placed the two Apple/factory shipped 1GB sticks in the bottom riser (2GB) for a total of 6GB of memory.

    The article states: "Some of you just want to buy two 2GB FB-DIMMs to add to the two factory 1GB FB-DIMMs for a total of 6GB. That configuration will slow you down. Don't do it. Again, the BEST performance setup is eight matched FB-DIMMs. The second best is four matched FB-DIMMs."

    Should I purchase additional Two x 2GB sticks so I have 4 matched FB-DIMMS? - Two x 2GB on the top riser and Two x 2 GB on he bottom riser?

    According to the barefeats article, I could still use the original 1GB sticks in the top riser slots 3 and 4 without slowing things down... For a total of 10GB

    Lumpy
     
  2. Pressure macrumors 68040

    Pressure

    Joined:
    May 30, 2006
    Location:
    Denmark
    #2
    Xbench is highly arguably as a usable benchmark utility to begin with.

    It is much more important that you have sufficient memory for your usage-pattern.
     
  3. netdog macrumors 603

    netdog

    Joined:
    Feb 6, 2006
    Location:
    London
    #3
    Barefeets is not the only one to report this. I installed 4x2GBs and pulled my stock 2x1GBs for this very reason (see auction in signature).

    You can etiher just pull your 2x1GBs or order two more 2x1GBs and install a total of 12GBs. That should perform very well, as long as groups of 4 FB-DIMMS are matched.
     
  4. ErikAndre macrumors 6502a

    ErikAndre

    Joined:
    Nov 14, 2007
    Location:
    Florida
    #4
    Glad you mentioned this... I was going to order 2x4GB to make 10GB RAM for future expandability. Should I order the 4x2GB instead?
     
  5. tersono macrumors 68000

    tersono

    Joined:
    Jan 18, 2005
    Location:
    UK
    #5
    In theory yes, your best performance will be with matched memory. However, the chances that you'd notice a real-world difference in normal use are pretty small IME.

    Remember: there's lies, damn lies and then there's benchmarks ;) :p
     
  6. netdog macrumors 603

    netdog

    Joined:
    Feb 6, 2006
    Location:
    London
    #6
    In your experience?

    Which Mac Pro are you using and what memory configs have you used for a prolonged period to give this assertion some weight?

    This memory issue only applies to the Mac Pro. MacBooks have their own issues with matched sticks because of the shared graphics RAM. MBPs really don't care.

    Every benchmark test I have read regarding the Mac Pro that addresses the issue of how to configure memory has found in tests that there is quite a difference.
     
  7. netdog macrumors 603

    netdog

    Joined:
    Feb 6, 2006
    Location:
    London
    #7
    That's what I chose to do. Yes. Of course, you could also order 4x4GB sticks. :eek:

    As mentioned earlier, you could also by two more 1GB sticks for a total of 12GB (with the 4x2GB sticks installed).
     
  8. Umbongo macrumors 601

    Umbongo

    Joined:
    Sep 14, 2006
    Location:
    England
    #8
    Which benchmarks? The only two I have seen relating to the Mac Pro were from anandtech and barefeats and both conclude that it doesn't much matter for real world performance.

     
  9. eviltobz macrumors member

    Joined:
    Nov 12, 2007
    #9
    ooooooh.
    /clicks "watch this item"
     
  10. LostSunrise macrumors member

    Joined:
    Sep 22, 2006
    #10
    Ok I'll bite...

    Like so many people I ordered 2-4 of the 2gb dimms and plan to add it to the stock 2. However I currently have on order 2x2gb of OWC certified, and 2x2gb of RAMJET (diversifying my chances of getting it with the computer). Could the brands minute differences be a factor if I yanked the stock 2gb and just used this batch or should I cancel the RAMJET order and get in the back of the line for more owc RAM. What is the main factor in this performance difference. I'm assuming its the size of the module. Help QUICK I need to act fast!
     
  11. LostSunrise macrumors member

    Joined:
    Sep 22, 2006
    #11
    Answer..

    I emailed Rob-Art at Barefeet and posed my question about mixing brands to him and he came back (quite quickly) with this answer.

    You'll want to check to see if the RAMJET memory has,
    a) CAS 5-5-5 rating and,
    b) Apple certified rating, and
    c) Apple approved heat sink

    If all the above is true, they should play nice with the OWC memory.
     
  12. CalfCanuck macrumors 6502a

    Joined:
    Nov 17, 2003
    #12
    This brings to mind the saying: "There are 3 types of lies - lies, damn lies, and statistics."

    The key question is slows you down RELATIVE TO WHAT? On a pure memory test, you will have a speed hit relative to the optimal configuration they tested. But in real world use, where memory speed is usually not the bottleneck, a minor speed hit in memory is NOTHING compared to the OS having to cache something to the hard drive due to lack of memory. Caching memory is a HUGE speed hit.

    So back to the question - if you can only afford 4 GB of after market RAM, and you end up with 2 x 2 GB sticks combined with the stock 2 x 1 GB, the system will run MUCH faster with this 6 GB configuration than leaving out the stock RAM and running with 4 GB.

    And even putting in 8 GB (4 x 2), the system will run faster in real use when you leave in the odd pair of stock RAM to end up with 10 GB. (Barefeats even tells you how to properly configure this 10 GB option at the bottom of the artlicel you linked to.
     
  13. ErikAndre macrumors 6502a

    ErikAndre

    Joined:
    Nov 14, 2007
    Location:
    Florida
    #13
    This now has got me thinking and a bit paranoid... what slots do i place these pupplies in and in what bays? Maybe like this?

    Bay 1
    Slot 1: 2gb
    Slot 2: 2gb
    Slot 3: 1gb
    Slot 4: Empty

    Slot 2
    Slot 1: 2gb
    Slot 2: 2gb
    Slot 3: 1gb
    Slot 4: Empty


    or....
     
  14. rockinrocker macrumors 65816

    rockinrocker

    Joined:
    Aug 21, 2006
    #14
    my guess is:
    Riser 1
    2
    2
    1
    1

    riser 2
    2
    2
    0
    0
     
  15. TheThirdMan macrumors regular

    TheThirdMan

    Joined:
    Nov 14, 2007
    Location:
    London, UK
    #15
    For best performance, you should get paired doubles. So each ram module should be the same size and the total number should be a multiple of 2. So 2x1, 4x1, 4x2 etc. If you don't do this, the speed penalty may not be noticeable, but if you have a complete mix, it may be significant.

    Having said this, im still going to have 2x2 and 2x1 in my mac pro....
     
  16. Jupeman macrumors member

    Joined:
    Jan 13, 2008
    #16
    I believe this is what the barefeats article says to do.
     
  17. netdog macrumors 603

    netdog

    Joined:
    Feb 6, 2006
    Location:
    London
    #17

    I think that's right. As mentioned before, better if you fill both slot 4s with 1gb pieces or leave slot 3s empty.
     
  18. GoKyu macrumors 65816

    GoKyu

    Joined:
    Feb 15, 2007
    Location:
    New Orleans
    #18
    I was going to ask about this as well...When I just had 2 gigs in there, the machine booted in like 30 seconds, but as soon as I put the extra 4 gigs in (2x2), now it takes over a minute to boot up (uh, not that I'm probably ever gonna have to reboot this thing much...hehe)

    Ok, so as soon as I can, I'll grab 2 more 2 gig sticks to make it 8...

    Netdog: If you can continue to use the extra 2 gigs without slowing down, why wouldn't you?

    Also, I thought I remembered reading somewhere that in order for Applecare to remain valid, you have to at least keep the Apple RAM and reinstall it when you bring it in to be serviced...

    -Bryan
     
  19. mrcandy macrumors regular

    Joined:
    Nov 12, 2007
    Location:
    Calgary, AB Canada
    #19

    It also happens to be what Apple recommends in the little brochure they ship with the MP. The ONLY configuration they show with non-matched pairs is the way they ship a standard 2GB config (1 stick in slot 1 of each riser). I have 10GB in my machine installed as shown above.
     
  20. CalfCanuck macrumors 6502a

    Joined:
    Nov 17, 2003
    #20
    While I think this was the recommended installation in the 2007 MP, I believe the barefeats post said that the early 2008 MP would only show RAM installed in this manner as 8 GB. If you put the 1GB in Slots 3 and 4, then the MP recognizes the full 10 GB.
     
  21. ErikAndre macrumors 6502a

    ErikAndre

    Joined:
    Nov 14, 2007
    Location:
    Florida
    #21
    Still sort of sucks tho... i wanted to buy 2x4Gb sticks (move to 10Gb) so I could expand later, but in order to satisfy this article, i have to buy 4x4Gb (which will tap the bank). Looks like I'm stuck with getting 4x2Gb and clutter the slots.

    [​IMG]
     
  22. netdog macrumors 603

    netdog

    Joined:
    Feb 6, 2006
    Location:
    London
    #22
    It might bust the bank, but you gotta admit...4x4 would be pretty sweet.
     
  23. ErikAndre macrumors 6502a

    ErikAndre

    Joined:
    Nov 14, 2007
    Location:
    Florida
    #23
    Indeed... but the bank has been very generous this year (with a 3.0MP, 8800GT and a 8GB upgrade)... i have plenty of leash here, but i don't want to push it, if you know what i mean. :rolleyes:
     
  24. desenso macrumors 6502a

    desenso

    Joined:
    May 25, 2005
    #24
    Sounds like the bank has a whip.
     
  25. deathshrub macrumors 6502

    Joined:
    Oct 30, 2007
    Location:
    Christmas Island
    #25
    Stop giving advice because you have no idea what you're talking about.
     

Share This Page