Question About Installing RAM

[Hastings101]

I currently have an iMac 27" i3 from mid 2010 with 4GB of RAM. If my current RAM setup is 2x2 (2 sticks of 2GB RAM) would adding RAM in any of these ways cause problems?

1 stick of 4GB RAM
2 sticks of 2GB RAM
2 sticks of 4GB RAM

I know this has probably been asked but I wanted a clear and specific answer. I know how to install RAM but I don't really understand anything beyond that.

 

[btbrossard]

It would be best to install the ram in pairs for best performance.

Here's some notes on adding ram from Apple:

Additional notes i5 and i7 Quad Core iMac computers come with both top memory slots populated. These computers will not start up if only a single DIMM is installed in any bottom slot; these computers should operate normally with a single DIMM installed in any top slot. Core Duo iMac computers should operate normally with a single DIMM installed in any slot, top or bottom. ("Top" and "bottom" slots refer to the orientation of the slots in the pictures below. "Top" refers to the slots closest to the display; "bottom" refers to the slots closest to the stand).

http://support.apple.com/kb/HT1423?viewlocale=en_US