Hi, they should be compatible. The motherboard says it supports socket type am3 and that Phenom II x4 840 says it is an AM3 so it should fit with no problems. http://shop.amd.com/US/_layouts/sho...y:Processor&filter=processor:AMD+Phenom+II+X4 http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=6766814&CatId=4296
That's clear, but there is not Phenom II x4 840 in the list of compatible CPUs. But actually it does not matter anymore: I decided to buy another things: Phenom II x4 955 + MSI 770-C45. Anyway thanks for reply.