Server/Requirements/Server

Since Minecraft rarely uses more than 3 threads, consider possible waste when buying more than 4 cores. However this does not apply to mods and plugins which utilize their own threads - buy accordingly. Assume that most of the server's load will be on a single core. The main performance factor is without a doubt CPU clock speed. CPU cache sizes and RAM latency are also factors. There does not appear to be a disadvantage to using high-end desktop processors.(verify?)

Win 2008

 * Note that these requirements are for the server only you will need to allocate more resources to the OS!

Console

 * Note that these requirements are for the server only you will need to allocate more resources to the OS!