MacBook Pro (2008) RAM only showing 3GB when 4GB is limit

Discussion in 'Mac Basics and Help' started by tbrennan3613, Jul 9, 2010.

  1. tbrennan3613 macrumors newbie

    May 27, 2008
    Hello. I recently upgraded my MBP's HDD and RAM. The HDD upgrade from 200GB 5400 to 320GB 7200 when great, however, I installed 4GB of matched RAM and only 3GB show up. The sticks are 2GB DDR2 667MHz. When I install 3GB (1GB & 2GB Sticks), only 2GB show up. I understand some MBP's have a 3GB limit, however, Apple told me the limit on my MBP is 4GB's. Any help would be appreciated. Thanks.

    I also tried 2 different brands of 4GB sticks (2X2GB)
  2. Makosuke macrumors 603

    Aug 15, 2001
    The Cool Part of CA, USA
    I'd have suggested that you didn't have the model you thought you did, since as you noted only being able to use 3GB of 4GB installed is the expected behavior on the pre-Santa Rosa ("Late 2006") MBPs.

    But if you only see 2GB usable when you've got 1G+2G installed, then something else must be wrong.

    Question: Does System Profiler show the correct RAM installed? That is, does it show a 2GB module in each slot, or is one of the 2GB modules showing up as 1GB even in System Profiler (normally, even if the computer can't address the memory, System Profiler will recognize it is installed correctly).

    The other thing is to see if it's a specific slot: Try putting 1GB in one slot and 2GB in the other, see what happens, and then swap the two so that the 1GB stick is in the other slot. If the behavior is different depending on which slot has the 1GB and 2GB module, that points to a problem with the slot. If it doesn't matter, must be something else.
  3. tbrennan3613 thread starter macrumors newbie

    May 27, 2008
    MBP Ram Issue.

    Hello. I am very sorry about the late reply, I entered an old email address in my MacRumors Forum settings.

    I purchased this MBP April 2007. It had 2GB Ram. I just placed 2X2GB in it of matched ram and it only shows 3GB.

    If I put any 1GB+2GB Sticks in (either slot), it only shows 2GB.

    I just want to verify that there is no way for this machine to use 4GB Ram?

    Thanks Again.
  4. J the Ninja macrumors 68000

    Jul 14, 2008
    April 2007? Yeah, your machine only supports 3GB. Design limitation of the chipset, nothing you could do about it.
  5. tbrennan3613 thread starter macrumors newbie

    May 27, 2008

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