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I've been using my MaBook Pro happily for months but only recently realized that 1 GB is missing. Is there something wrong with my MacBook? It seem to runs fine.

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What MacOSX version? I have a very similar problem. Though I could access all the 4GB under MacOSX 10.5 -- I only have the problem since MacOSX 10.6. – Albert May 12 '10 at 22:28
up vote 7 down vote accepted

Usually this is because you're using a 32-bit operating system rather than a 64-bit one.

UPDATE: Apparently, this is a chipset limitation in the earlier Macbook Pros

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No - my wife's MBP can only address 3Gb, and mine can address 4Gb, and we're running exactly the same OS. – Paul Tomblin Jul 21 '09 at 2:07
Updated my answer. – Stefan Thyberg Jul 21 '09 at 2:13
Good. Removed my downvote. – Paul Tomblin Jul 21 '09 at 11:00
Thanks guys for your answers. – user3092 Jul 21 '09 at 13:45

Which MBP? My wife's 3 year old 15" MBP has a published maximum memory of 3Gb. My 1.5 year old 17" MPB has a published maximum memory of 4Gb.

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