Intel 64 and IA-32 Architectures Software Developers Manual Volume 1, Basic Architecture

Vol. 1 4-11
DATA TYPES
4.6 PACKED SIMD DATA TYPES
Intel 64 and IA-32 architectures define and operate on a set of 64-bit and 128-bit
packed data type for use in SIMD operations. These data types consist of funda-
mental data types (packed bytes, words, doublewords, and quadwords) and numeric
interpretations of fundamental types for use in packed integer and packed floating-
point operations.
4.6.1 64-Bit SIMD Packed Data Types
The 64-bit packed SIMD data types were introduced into the IA-32 architecture in the
Intel MMX technology. They are operated on in MMX registers. The fundamental
64-bit packed data types are packed bytes, packed words, and packed doublewords
(see Figure 4-7). When performing numeric SIMD operations on these data types,
these data types are interpreted as containing byte, word, or doubleword integer
values.
Figure 4-7. 64-Bit Packed SIMD Data Types
Packed Words
Packed Bytes
Packed Doublewords
0
63
0
63
0
63
Packed Word Integers
Packed Byte Integers
Packed Doubleword Integers
0
63
0
63
0
63
Fundamental 64-Bit Packed SIMD Data Types
64-Bit Packed Integer Data Types