User Guide

xxiv Preface
AMD64 Technology 24592—Rev. 3.15—November 2009
Software must not depend on the state of a reserved field, nor upon the ability of such fields to
return to a previously written state.
If a reserved field is not marked with one of the above qualifiers, software must not change the state
of that field; it must reload that field with the same values returned from a prior read.
REX
An instruction prefix that specifies a 64-bit operand size and provides access to additional
registers.
RIP-relative addressing
Addressing relative to the 64-bit RIP instruction pointer.
scalar
An atomic value existing independently of any specification of location, direction, etc., as opposed
to vectors.
set
To write a bit value of 1. Compare clear.
SIB
A byte following an instruction opcode that specifies address calculation based on scale (S), index
(I), and base (B).
SIMD
Single instruction, multiple data. See vector.
SSE
Streaming SIMD extensions instruction set. See 128-bit media instructions and 64-bit media
instructions.
SSE2
Extensions to the SSE instruction set. See 128-bit media instructions and 64-bit media
instructions.
SSE3
Further extensions to the SSE instruction set. See 128-bit media instructions.
SSE4A
Further extensions to the SSE instruction set. See 128-bit media instructions.
sticky bit
A bit that is set or cleared by hardware and that remains in that state until explicitly changed by
software.
TOP
The x87 top-of-stack pointer.