6 - 8 GB Ram = Dual channel loss?

Discussion in 'MacBook Pro' started by MBX, Oct 15, 2008.

  1. MBX macrumors 68000

    Sep 14, 2006
    Can anybody tell me if it's true that with 6-8gb of ram you lose dual-channel that hurts 3d applications the most?

    is it the case with 6 too or only with 8gb of ram in the mbp's?
  2. alphaod macrumors Core


    Feb 9, 2008
    Well it depends. If you can find 3GB sticks to make 2x3GB, you still still have dual channel, but since the only option is really 2GB+4GB, then yes you lose dual channel. With 8GB, it's 2x4GB, so it's dual channel as well.

    Finally the difference in dual channel and not is very miniscule.
  3. MBX thread starter macrumors 68000

    Sep 14, 2006
    so would you advise to go with 1x2GB and 1x4GB (=6GB) or 2x4GB (=8GB)?

    i heard that 8gb slows things down tremendously (?) in os-x if it goes over 4gb but not so when booted in vista. Which is really strange since apple says os-x is 64bit and best os ever blah blah.
  4. alphaod macrumors Core


    Feb 9, 2008
    Yes it slows down when you install 8GB on the SR MBP; not sure about the new ones though. Also OS X is 64-bit; how else would Mac Pros use up to 32GB of RAM. ;)
  5. MBX thread starter macrumors 68000

    Sep 14, 2006
    anybody with experience and having tested 6gb in mbp's can confirm if the difference is 'miniscule'?

    is there anywhere a benchmark yet?

  6. Tweak3D macrumors regular

    Jul 17, 2007

    already been tested,its a very small difference and if you are paging out alot or using programs like photoshop or something using lots of ram you will gain speed through having the extra memory.
  7. dal20402 macrumors 6502

    Apr 24, 2006
    If you need the RAM, you need the RAM.

    Even a small amount of swapping is going to constitute a vastly bigger performance hit than any loss of memory bandwidth from not having dual channel.
  8. MBrolling macrumors member

    Sep 6, 2008
    Can anyone help with this situation. http://www.mwave.com/mwave/viewprod...&updepts=NBMEMORY-DDR2&DNAME=NB+Memory+-+DDR2

    I want to upgrade my pro to 4 gigs of those corsair ram. I noticed that buying single 2 gig sticks would be cheaper than the 4 gig kit they offer. If i buy 2 of the single 2gig sticks, i should still be getting dual channel right? I was thinking there would really be no difference in the two, but someone told me that the 4gig kit would be dual channel since they are packaged together and are same exact ram, and that getting 2 of the 2 gig sticks would not give dual channel or be the same. any comments on that?
  9. MBX thread starter macrumors 68000

    Sep 14, 2006
    hey i just wanted to say that i installed my g-skill 4gb module today and now have my mbp running at 6gb of ram.

    absolutely fantastic!

    i have not noticed any slow downs or anything related to dual channel and i tested 3d programs and such too.

    very happy about the speed gain.
  10. kolax macrumors G3

    Mar 20, 2007
    Speed gain?

    What are you doing with your Mac that you need 6GB's? Speed gain with what applications?
  11. MBX thread starter macrumors 68000

    Sep 14, 2006
    hey it's not 2004 anymore where 4gb were enough for everybody :)

    actually even 6gb isn't my optimal config. if i could put in 8-16gb in my macbook pro i would.

    there are many of us who use ram intensive apps like pornoshop or 3d stuff.
  12. 7even macrumors 6502a

    Jan 11, 2008
  13. Firefly2002 macrumors 65816

    Jan 9, 2008
    ROFL! Holy hell, that's the worst Freudian slip I've ever seen. Talk about incriminating. You sure you don't just surf porn when you're supposed to be working? XD

    Also, I think Alpha meant to say the dual-channel speed increase IS miniscule.... because, well, it is.
  14. evilzardoz macrumors newbie

    Oct 19, 2008
    alphaod - PAE will use extended addressing to permit 32GB on any 32bit system. Windows Server Enterprise and Datacentre uses this technology.

    I have a pair of G.Skill modules (8GB) and I need to determine whether this is a chipset limitation or not. Unfortunately I don't know how to disable dual channel operation as I suspect it's a combination of >4GB RAM *AND* dual channel operation. 6GB configurations only use the first 4GB in dual-channel mode. The only way to get more than 4GB in dual-channel mode is to get 4GB modules.

    Maybe I'll install a 64-bit OS under Bootcamp to test this further; however I suspect the issue may also be an OSX thing.

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