It is ok to put a different size in that second slot.
Apple, and a lot of other companies, say that you will get better performance if both the slots contain identical RAM.
Increasing your RAM by 2GB is going to give you an edge and I doubt that you will even notice the difference in performance, apart from the speed boost.
Go ahead and do it.
P
I have an iMac (20", OS X 10.4.11) purchased a few months ago and I'd like to add some more memory. It has 1GB. Is it okay to put a 2GB card in the other slot, or should they match in size; i.e., two 1GB cards, not one 1GB and one 2GB?
TIA

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