SSE2 is the second SIMD instruction set designed by Intel. SSE2 was added to the IA32 instruction set with the release of the Pentium 4 CPU in 2001.

SSE2 adds support for 64 bit double precision floating point and for 64, 32, 16 and 8 bit integer operations using the eight original 128 bit XMM registers. SSE2's integer instructions largely replace the need to use the older MMX instruction set. But SSE2 does not completely replicate MMX's total functionality.