AltiVec — An OverviewAltiVec is a SIMD instruction set developed by Apple around 1998. It is a floating-point instruction set used in PowerPC microprocessors. It operates on 32-bit floating point numbers, as well as 8, 16, and 32-bit integers. It provides 32 registers which are 128 bits wide. AltiVec is related to VMX, which was developed by IBM.
A good overview of the AltiVec instruction set can be found here: