AMD-K6-2E/400AFR AMD [Advanced Micro Devices], AMD-K6-2E/400AFR Datasheet - Page 42

• Manufacturer Part Number: AMD-K6-2E/400AFR
• Manufacturer: AMD [Advanced Micro Devices]

AMD-K6™-2E Processor Data Sheet
General-Purpose
Registers
Figure 7. EAX Register with 16-Bit and 8-Bit Name Components
24
31
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. General-Purpose Registers
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 AL (low
order bits). The same naming convention applies to EBX, ECX,
and EDX.
EDI, ESI, ESP, and EBP can be used as smaller 16-bit registers
called DI, SI, SP, and BP respectively, but these registers do not
have 8-bit versions. Figure 7 shows the EAX register with its
name components, and Table 3 on page 25 lists the doubleword
(32-bit) general-purpose registers and their corresponding word
(16-bit) and byte (8-bit) versions.
Register Function
EDX
EAX
EBX
ECX
ESP
EBP
EDI
ESI
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
Preliminary Information
Software Environment
16
EAX
15
AH
8
AX
7
22529B/0—January 2000
AL
Chapter 3
0