User Guide

64-Bit Media Programming 201
24592—Rev. 3.15—November 2009 AMD64 Technology
5.5 Operands
Operands for a 64-bit media instruction are either referenced by the instruction's opcode or included as
an immediate value in the instruction encoding. Depending on the instruction, referenced operands can
be located in registers or memory. The data types of these operands include vector and scalar integer,
and vector floating-point.
5.5.1 Data Types
Figure 5-8 on page 202 shows the register images of the 64-bit media data types. These data types can
be interpreted by instruction syntax and/or the software context as one of the following types of values:
• Vector (packed) single-precision (32-bit) floating-point numbers.
• Vector (packed) signed (two's-complement) integers.
• Vector (packed) unsigned integers.
• Scalar signed (two's-complement) integers.
• Scalar unsigned integers.
Hardware does not check or enforce the data types for instructions. Software is responsible for
ensuring that each operand for an instruction is of the correct data type. Software can interpret the data
types in ways other than those shown in Figure 5-8 on page 202—such as bit fields or fractional
numbers—but the 64-bit media instructions do not directly support such interpretations and software
must handle them entirely on its own.