12 gigs of ram possible?

Discussion in 'iMac' started by jvdrummer182, Jul 31, 2010.

  1. jvdrummer182 macrumors regular

    Jun 18, 2010
    Will my 27" i7 iMac run with 12 gigs of ram? The computer came with 2 x 2 gb cards and I am looking to add 2 x 4 gb ram cards.
  2. celticpride678

    Feb 15, 2009
    Boston, MA
    According to Apple, the new iMac can support up to 16 GB of RAM, but I think you're going to have to run Snow Leopard in 64-bit mode for it to recognize all the RAM.
  3. flopticalcube macrumors G4


    Sep 7, 2006
    In the velcro closure of America's Hat
    It will run 12GB no problem. The kernel does not have to be 64bit to utilize it, such is the dual nature of Snow Leopard.
  4. JoelMarcey macrumors 6502


    Jun 9, 2009
    Northern California
    I am running with a nice 12GB in my i5 as I type this.
  5. Sun Baked macrumors G5

    Sun Baked

    May 19, 2002
    All depends on the number of bits the chipset uses for the address bus, even though people toss around 64-bit EFI and trot out other numbers.

    If the chipset is 32-36 bits for the address bus it'll have a limit far lower than the OS, while the workstations are running somewhere around a 40-bit memory address.

    Even though most Intel CPU can support 36-40 bits, the chipset might only allow 8-16GB of ram, so the bit support is far below what the CPU can handle.

    Intel wants us to upgrade, so they are adding bits to memory support rather slowly to the chipsets.
  6. Thermonuclear macrumors 6502

    May 23, 2009
    FYI: The Intel Core i3 CPUs as used in the new iMacs are limited to 16 GB RAM as per the specifications on Intel's web site. That's 34 bits of physical addressing.

    Sad to say, all of our modern computers would be far more powerful if only developers could get a grip on reducing software bloat. It was more than thirty years ago that I learned Unix on a Digital pdp-11/70 that had only 22 bits of addressing (4 MB core RAM). And there were always multiple users on the timeshared machine.
  7. aliensporebomb macrumors 68000


    Jun 19, 2005
    Minneapolis, MN, USA, Urth
  8. dexthageek macrumors 6502

    Dec 7, 2007
    yeah it works fine. Just make sure you get the right ram for your machine. The 2009 and 2010 machines use different ram.

    2009 - PC-8500 1066Mhz CL 7
    2010 - PC-10600 1333Mhz CL 9
  9. pommack macrumors newbie

    Feb 19, 2010

    Any ideas does the new 1333Mhz memory work in 2009 models?

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