User Guide

Preface xix
24592—Rev. 3.15—November 2009 AMD64 Technology
32-bit mode
Legacy mode or compatibility mode in which a 32-bit address size is active. See legacy mode and
compatibility mode.
64-bit mode
A submode of long mode. In 64-bit mode, the default address size is 64 bits and new features, such
as register extensions, are supported for system and application software.
#GP(0)
Notation indicating a general-protection exception (#GP) with error code of 0.
absolute
Said of a displacement that references the base of a code segment rather than an instruction pointer.
Contrast with relative.
ASID
Address space identifier.
biased exponent
The sum of a floating-point value’s exponent and a constant bias for a particular floating-point data
type. The bias makes the range of the biased exponent always positive, which allows reciprocation
without overflow.
byte
Eight bits.
clear
To write a bit value of 0. Compare set.
compatibility mode
A submode of long mode. In compatibility mode, the default address size is 32 bits, and legacy 16-
bit and 32-bit applications run without modification.
commit
To irreversibly write, in program order, an instruction’s result to software-visible storage, such as a
register (including flags), the data cache, an internal write buffer, or memory.
CPL
Current privilege level.
CR0–CR4
A register range, from register CR0 through CR4, inclusive, with the low-order register first.
CR0.PE = 1
Notation indicating that the PE bit of the CR0 register has a value of 1.