Hi, 1) Seems that all defintions for MMX, SSE and SSE2 are deinred in mmtrin.h,xmmintrin.h and emmintrin.h header files respectively. Am I right? 2) In those header files all functions call _builtin_ia32_*. Where those functions(body) are defined? 3) I thought that associated with each SIMD instruction defined in Intel-ia-32-architectures manual(Basic architecture) there is one function defined in those header files. But for some instructions no functions were defined in those header files.(For example MOVDQA instruction) Also those header files contain some more functions for which no SIMD assembly instruction exist.Example in emmintrin.h static __inline __m128i _mm_load_si128 (__m128i const *__P) { return (__m128i) __builtin_ia32_loaddqa ((char const *)__P); } What could be the reason? Thanks in advance. ___________________________________________________________ To help you stay safe and secure online, we've developed the all new Yahoo! Security Centre. http://uk.security.yahoo.com