the width of the simd register file is increased from 256 bits to 512 bits, and expanded from 16 to a total of 32 registers zmm0-zmm31. these registers can be addressed as 256 bit ymm registers from avx extensions and 128-bit xmm registers from streaming simd extensions, and legacy avx and sse instructions can be extended to operate on the 16 additional registers xmm16-xmm31 and ymm16-ymm31 when using evex encoded form.