Apple's RAM limit real or “marketing”?

Question

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.)

Answer 1

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

Answer 2

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.