SSE
From Avisynth wiki
SSE is a new instruction set (set of processor commands) present in most modern processors such as P3, P4, newer Celerons, Athlon XP, MP. It is an extension of the MMX instruction set. A subset of SSE to operate on integers, Integer SSE (or ISSE for short) is of special interest to Avisynth plugins developers because it is mostly used for video processing.