Chapter 10 Instruction Set: Charateristics and Functions

Instruction Set:
The collection of instructions that a CPU can execute:

The instruction set determines the function of CPU

Element of an instrction
Operation code(Op code)
Source operand reference
Result operand reference
Next instruction reference

Operands are stored in cache or main memeory or virtual memory, CPU registers, I/O devices.

Instruction types:
Data processing 
Data storage(main memory)
Data movement(I/O)
Program flow control: test and branch

Number of addresses
4 addresses

A4 is next instruction address

3 addresses

Next instruction address is usually implicit

2 addresses

1 address

Implicit second address: usually a register(accumulator, AC)

0 address: Op code

All addresses are implicit or no address
Uses a stack

Types of operands
Address
Numbers
Characters
Logical data

Types of operations
Data transfer: the most fundamental

Specify

Source
Destination: registers, memory, top of stack
Amount of data
Mode of addressing

Arithmetic
Logical
Conversion

Translate: some values in memory are converted by table query
Convert: base conversion

I/O
System control
Transfer of control

MMX: A set of highly optimized instructions for multimedia applications
SIMD execution model

SIMD allows the same operation to be carried out on multiple data elements in parallel. The MMX technology supports parallel opertions on byte, word, and doubleword data elements which contained in MMX registers.

Wraparound & Saturation arithmetic

Wraparound arithmetic: the extra bit is truncated when overflow occurs.
Saturation arithmetic: When overflow or underflow happens, the result is set to the largest or smallest value representable