Minimum CPU needed

From FaHWiki

There is no lower limit for CPU speed in FAH. If the hardware will run Windows or Linux, it should run FAH. However, the slower the machine, the longer FAH will take to finish work units (WUs). The general trend is to have faster and faster CPUs to tackle the ever growing size of WUs. The current minimum CPU that is recommended (on the forums, not by the project) is a 500MHz Pentium III.

CPUs slower than 500 MHz are probably too slow to complete WUs unless the machine is running 24x7 (such as a router or print-server), and SIMD extensions are basically a must.