Just take a look at the webpage of the manufactor of the processors.
AMD:
http://www.amd.com/us-en/Processors/...30_118,00.html
Athlon/Sempron are desktop processors, not designed to power a server.
Server processor = Opteron
Intel:
http://www.intel.com/products/proces...uct_Processors
Itanium 2, most Xeon's, and high-end Pentium-4/D are designed as server processor.