User Guide

Preface xxi
24592—Rev. 3.15—November 2009 AMD64 Technology
FF /0
Notation indicating that FF is the first byte of an opcode, and a subopcode in the ModR/M byte has
a value of 0.
flush
An often ambiguous term meaning (1) writeback, if modified, and invalidate, as in “flush the cache
line,” or (2) invalidate, as in “flush the pipeline,” or (3) change a value, as in “flush to zero.”
GDT
Global descriptor table.
GIF
Global interrupt flag.
IDT
Interrupt descriptor table.
IGN
Ignore. Field is ignored.
indirect
Referencing a memory location whose address is in a register or other memory location. The
address may be an absolute or relative address. Compare direct.
IRB
The virtual-8086 mode interrupt-redirection bitmap.
IST
The long-mode interrupt-stack table.
IVT
The real-address mode interrupt-vector table.
LDT
Local descriptor table.
legacy x86
The legacy x86 architecture. See “Related Documents” on page xxviii for descriptions of the
legacy x86 architecture.
legacy mode
An operating mode of the AMD64 architecture in which existing 16-bit and 32-bit applications and
operating systems run without modification. A processor implementation of the AMD64
architecture can run in either long mode or legacy mode. Legacy mode has three submodes, real
mode, protected mode, and virtual-8086 mode.