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macnicol

macrumors member
Original poster
Mar 1, 2006
52
27
My late 2009 27in iMac that just "died", probably the power supply, it has 16gb of 1066MHz DDR3 SDRAM. I'm looking at replacing it with a mid 2011 27in iMac which has 4GB 1333MHz DDR3 SDRAM. Can I use the 1066MHz DDR3 SDRAM in place of the 1333MHz DDR3 SDRAM? I realize this would probably be a downgrade in overall system speed, but will it work?
 

keysofanxiety

macrumors G3
Nov 23, 2011
9,539
25,302
Not sure why the user above said nope. You definitely can use slower RAM in a machine which has faster stock RAM. It'll just run at the slower speed (1066MHz vs 1333MHz).
 

EugW

macrumors G5
Jun 18, 2017
14,977
12,941
Not sure why the user above said nope. You definitely can use slower RAM in a machine which has faster stock RAM. It'll just run at the slower speed (1066MHz vs 1333MHz).
I believe that may be true for the 2011 iMac.

However, that is not true for all Macs. Some Macs will just refuse to boot.
 

DeltaMac

macrumors G5
Jul 30, 2003
13,767
4,591
Delaware
If you have the RAM now, you can certainly try it.
If it boots, and seems to work normally --- and also passes the Diagnostics test, then great. The memory bus will operate at the speed of the slowest RAM installed, but if it works, use it.
(It's entirely possible that a failing power supply can damage installed RAM sticks - I've seen it happen before, so don't go in with the expectation that RAM that you might pull out of a dead iMac is good... That remains to be seen (and tested!)
 
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