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I have a 21.5" iMac (Late 2009). Apple says that this can handle up to 8GB of RAM. They say that the 27" can handle more (up to 16GB). What happens if I install 16GB? Will it run? Crash? Use only part of it?

EDIT:

I finally called and chatted with Apple (simultaneously) and at first they said that the max is 8GB. After I showed them those documents, they agreed with me. the max is 16GB. (Thanks, Spiff.)

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Does the 27" iMac have the same number of RAM slots, as your 21.5" iMac? –  mctylr Apr 1 '10 at 16:31
    
@mctylr - Yes, it does. Same speed too. –  Moshe Apr 1 '10 at 22:51
    
You know, Apple will gladly sell you 16GB of RAM at $100 per GB. Plus shipping, of course... –  Joe Internet Apr 2 '10 at 2:56
    
@Joe Internet, sure they would. Where is it cheaper? $100 for a 4GB stick is cheap. (In terms of DDR3 anyways...) –  Moshe Apr 2 '10 at 15:15
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Weel, it looks like Apple is selling 4GB upgrades for $200...store.apple.com/us/memorymodel/ME_IMAC_F09_21. You can do better at Newegg...newegg.com/Product/… –  Joe Internet Apr 2 '10 at 15:47

2 Answers 2

up vote 4 down vote accepted

Here are some places where Apple says it supports 16GB of RAM:

http://www.apple.com/imac/specs.html

(The information at the link above still applies to your model temporarily since a new model has not come out yet. The link below is always for your specific model.)

http://support.apple.com/kb/SP576

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As per your links Apple admitted that I need not buy new 27" iMac to get the benefit of buying 16GB of RAM from them. –  Moshe Apr 2 '10 at 15:14

Typically one of two things happen:

  1. It works--sometimes the memory controller can handle that much memory but it was never tested in an official capacity.

  2. It doesn't--the chipset can't address the extra memory and you will hit the 8GiB limit. The old Apple machines did this (LC II only seeing 10MiB, anyone?)

  3. It catastrophically doesn't--the chipset addresses a significant subset of the memory. You may only see 4GiB.

Best thing to do is to try.

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