Instruction Set Architecture

September 27, 2016

What is Computer Architecture

Computer Architecture = Machine Organization (the bulk of the class) + Instruction Set Architecture

The Path Down

  1. High-Level Program
  2. Compiler
  3. Assembly Language Program
  4. Assembler
  5. Machine Code

The ISA

  • That part of the architecture that is visible to the programer:
    • opcodes (available instructions)
    • number and types of registers
    • instruction formats
    • storage access, addressing modes
    • exceptional conditions
  • Many models of processors can support one ISA.

Computer Architecture

  • Design the hardware to execute programs written in the ISA as fast as possible

Key ISA decisions

  • Operations
    • how many?
    • which ones
  • Operands
    • how many
    • location
    • types
    • how to specify?
  • Instruction format
    • size

Instruction Formats

  • Size
    • Fixed width (MIPS) vs. variable width
  • MIPS Instruction Formats
    • R:
    • I: Data Transfer Instruction
    • J: Jump