AMD-K6 AMD [Advanced Micro Devices], AMD-K6 Datasheet - Page 39

• Manufacturer Part Number: AMD-K6
• Description: AMD-K6 Processor
• Manufacturer: AMD [Advanced Micro Devices]

20695H/0—March 1998
3
3.1
General-Purpose
Registers
Chapter 3
Software Environment
Registers
This chapter provides a general overview of the AMD-K6
processor’s x86 software environment and briefly describes the
data types, registers, operating modes, interrupts, and
instructions supported by the AMD-K6 architecture and design
implementation.
The AMD-K6 processor contains all the registers defined by the
x86 architecture, including general-purpose, segment,
floating-point, MMX, EFLAGS, control, task, debug, test, and
descriptor/memory-management registers. In addition, this
chapter provides information on the AMD-K6 Model-Specific
Registers (MSRs).
Note: Areas of the register designated as Reserved should not be
The eight 32-bit x86 general-purpose registers are used to hold
integer data or memory pointers used by instructions. Table 2
contains a list of the general-purpose registers and the
functions for which they are used.
Table 2.
In order to support byte and word operations, EAX, EBX, ECX,
and EDX can also be used as 8-bit and 16-bit registers. The
shorter registers are overlaid on the longer ones. For example,
the name of the 16-bit version of EAX is AX (low 16 bits of
EAX) and the 8-bit names for AX are AH (high order bits) and
Register
EAX
EBX
ECX
EDX
EBP
ESP
EDI
ESI
modified by software.
Commonly used as an accumulator
Commonly used as a pointer
Commonly used for counting in loop operations
Commonly used to hold I/O information and to pass parameters
Commonly used as a destination pointer by the ES segment
Commonly used as a source pointer by the DS segment
Used to point to the stack segment
Used to point to data within the stack segment
General-Purpose Registers
Software Environment
Function
AMD-K6
®
Processor Data Sheet
21