iMac8.1 RAM Limit

Discussion in 'iMac' started by mixel, Mar 31, 2010.

  1. mixel macrumors 65816

    mixel

    Joined:
    Jan 12, 2006
    Location:
    Leeds, UK
    #1
    Hi! I have the 2.8Ghz 8800GS iMac8,1

    Theoretically the memory limit is 4GB, at least that's what Apple say, and the Macrumors guide. I've found a few mentions of people having upgraded it to 6GB (one 4GB and one 2GB) though. OWC say it works fine with 6GB. Everything I've seen sofar says it doesn’t boot or is unreliable with 8GB, so I'd avoid that unless someone can prove otherwise!

    I have 4GB in there already, but 6 would probably be handy for Aperture and Photoshop.. Maybe even games once Steam is here..

    Does anyone have 6GB in their iMac 8,1? It's a pretty expensive upgrade so I'd need to know it works first. :D
     
  2. mynewromantica macrumors regular

    Joined:
    Aug 3, 2009
    #2
    I have been curious about this too.
    If it can handle 6 GB is stable at that amount?
     
  3. rlewis52 macrumors newbie

    Joined:
    Sep 22, 2007
    #3
    Yes I put 6GB in my about a month ago and it works great and is faster loading 4CS and aperture.
     
  4. mixel thread starter macrumors 65816

    mixel

    Joined:
    Jan 12, 2006
    Location:
    Leeds, UK
    #4
    :D Thank you, that's great news! It'll help out with Blender too I'd imagine.

    Having 6GB might even make it worth using the 64bit kernel?

    Anyone else done this upgrade? I'm pretty sure I'm going to try it now!
     
  5. Hellhammer Moderator

    Hellhammer

    Staff Member

    Joined:
    Dec 10, 2008
    Location:
    Finland
    #5
    No. 64-bit kernel has nothing to do with RAM limits in OS X.
     
  6. mixel thread starter macrumors 65816

    mixel

    Joined:
    Jan 12, 2006
    Location:
    Leeds, UK
    #6
    I know it has nothing to do with the physical RAM limitation, I just thought the speed improvements brought by the 64bit Kernel might be increased by having a bigger pool of RAM? Maybe not.

    Seems according to http://macperformanceguide.com/SnowLeopard-Performance.html that it might always be worth me running the 64bit kernel anyway.

    Seems to contradict this: "It is important to know that there are no good reasons to run machines with less than 4 GB RAM in 64 bit mode. Snow Leopard runs 32/64it applications in both modes (look at Activity Monitor application). The only real differnce is that 32 bit mode cannot run 64 bit kernel extensions and vice versa (so VirtualBox and Parallels Desktop may not run in 64bit mode). Feel free to experiment with 64 bit technology." from http://www.thrull.com/corner/mac/SystemModeConfigurator/
     
  7. belvdr macrumors 603

    Joined:
    Aug 15, 2005
    #7
    The only way to tell is to try it; there's no definitive performance increase seen by moving to 64-bit. Performance increases vary based on hardware and application. In some cases, it can actually hinder performance.
     
  8. mixel thread starter macrumors 65816

    mixel

    Joined:
    Jan 12, 2006
    Location:
    Leeds, UK
    #8
    TY! With 4GB it doesn't make any visible difference. Not sure I'd notice a 5-10% speed increase anyway, it's pretty tiny. :) Aperture seems to hog the machine whatever you do anyway.

    I wonder what sort of performance increase I can expect with 6GB in general.
     
  9. gcthompson macrumors newbie

    Joined:
    Apr 6, 2010
    #9
    Incidentally, I've tried benchmarking my system with a 4Gb matched pair of Crucial SODIMMs (2x2Gb) and an unmatched pair (1x2Gb, 1x4Gb). The results are here:

    http://db.xbench.com/merge.xhtml?doc2=437012&doc1=437013

    How this actually affects the system however :) It seemed to affect the XP VM (running under VMware fusion 3.0) only when I changed the VM Size from 2Gb to 3Gb. Whether that's a coincidence or not is debatable, my VM is somewhat flakey at points.
     
  10. mixel thread starter macrumors 65816

    mixel

    Joined:
    Jan 12, 2006
    Location:
    Leeds, UK
    #10
    Yowza, when running the 64 bit version of Geekbench, with 6GB of Ram I get dramatically higher scores than pre-upgrade..

    4370pts - Higher than the average 3Ghz "Late 2009" iMac.. (mine's only 2.8Ghz)

    I got a good ~400 point bump by using the 64bit kernel. Everything seems to be running perfectly both with the 64bit kernel and the 6GB of ram.. Parallels boots quicker, I dont get any Page-outs anymore, everything's fine, nothing seems to be incompatible sofar.. :D

    I bought the ram from OWC as the UK places weren't in stock and was prepared to have to pay import taxes/VAT.. Neither of which happened. Bargain!

    The most obvious speed up though has been in Aperture. Very happy with this upgrade. :)
     
  11. greg400 macrumors 6502

    Joined:
    Aug 13, 2009
    #11
    That's because the processor in your machine has 6MB of L2 cache, the late 2009 iMac's with a 3.06 processor have 3MB of L2 cache despite the early 2009 iMacs having a 3.06 processor with 6MB of L2 cache.
     

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