I am running a Core 2 Duo ULV @ 1.2Ghz (I know, it's not much, but it's running 24/7)
Just to show the average load: http://img546.imageshack.us/img546/5223/screenshotfrom201304071.png
(Running Mint 14 x64, on all 2 Cores)
btw It has been folding for the whole uptime.