I have heard numerous stories about the amount of RAM needed for mining. When building my own rig I encountered problems when running 1 290x on 4gb RAM (Windows 7), an error showed up in cgminer. After pacing another 4gb the error disappeared.

Having this error is searched for info and saw many different views, varying from 2GB/GPU needed to people running 5x 290x on 4 GB of RAM.

I thought it might be caused by the operating systems that is used?

Please share your experience and expertise.