$ProcessorType

$ProcessorType is a string giving the architecture of processor on which Mathematica is being run.

Typical values are "x86", "PowerPC", "SPARC", "MIPS", "PA-RISC" and "AXP".

$ProcessorType specifies the basic instruction set used by the CPU of your computer.

Computers with the same $ProcessorType may not be binary compatible.

See The Mathematica Book: Section 2.13.5.

See also: $MachineType, $OperatingSystem, $System.