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I am trying to buy ram to upgrade a MacBook bought in Mid 2009. It is the 13 inch MacBook 5,2.

This document gives some specs on the ram. It says DDR2, but does anyone know if DDR3 will also work?

But I want to make sure I get the right thing. Looking for 2x2GB sticks for a total of 4GB. What should I look for in the RAM?

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up vote 3 down vote accepted
  1. DDR3 will not work in a machine that supports only DDR2. They're different technologies. In fact, DDR3 memory will not fit in DDR2 slots.

enter image description here

  1. Any memory that satisfies the requirements specified in the link you posted should do:

    4 GB    PC2-6400 DDR2 800 MHz Type RAM  MacBook (Mid 2009)
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thanks, ill accept your answer in about 8.5 minutes lol. – matt walters May 19 '12 at 21:12
MacBooks, like most notebooks work with SO-DIMMs, not with desktop memory modules. – user127350 May 19 '12 at 21:13
@Radoo oops. Editing my answer to fix that – Renan May 19 '12 at 21:14

As already suggested, DDR3 is incompatible with DDR2 slots.

Upgrading RAM in Macs can be tricky. I recently upgraded a MacMini of the same vintage (2009), and initially bought RAM that "matched" Apple's suggestion, only to discover that if I used both of the new DIMMs the system wouldn't boot. It needed a "good" chip it could pull timing data from (or some other piece of voodoo that I haven't fully researched) that the others didn't supply. Ordered another DIMM, this time from Crucial, and all was well.

You may check with Crucial first. I'm not absolutely recommending buying from them, but they do a very good job of researching and matching the RAM to the system.

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Is it possible the initial RAM you tried was just dead? – matt walters Feb 6 '13 at 5:57
The RAM itself worked as long as it wasn't in the first slot. No memcheck failures, either. But sure, maybe the "important" part of it was dead on both DIMMs? – cydonian.monk Feb 27 '13 at 21:35

It works with SO-DIMMs DDR2 not DDR3. They have, for one, different pins alignment. See this image.

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