SSE2, Streaming "Single Instruction, Multiple Data" Extensions 2, is one of the IA-32 SIMD instruction sets, first introduced by Intel with the initial version of the Pentium 4 in 2001. It extends the earlier version SSE instruction set, and is intended to fully supplant MMX. SSE2 has itself been extended by SSE3, also known as "Prescott New Instructions", introduced by Intel to the Pentium 4 in early 2004. It has 144 new instructions from SSE which has 70 instructions.
Rival chip-maker AMD added support for SSE2 with the introduction of their Opteron and Athlon 64 ranges of 64-bit CPUs in 2003, and in 2005 added support for the SSE3 instruction set with an updated "E" revision of their processors.