Super User is a question and answer site for computer enthusiasts and power users. It's 100% free, no registration required.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

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?


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.)

share|improve this question
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
Weel, it looks like Apple is selling 4GB upgrades for $ You can do better at… – Joe Internet Apr 2 '10 at 15:47
up vote 4 down vote accepted

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

(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.)

share|improve this answer
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.

share|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.