4. MIPS Instruction Set2

생성일: 2021년 9월 21일 오후 5:42

A Basic MIPS Instruction

1. C Code : a=b+c;
2. Assembly code : (human-friendly machine instructions)
   add a, b, c # a is the sum of b and c
3. Machine code : (hardware-friendly machine instructions)
   00000010001100100100000000100000

ISA

Instruction Set Architecture

• A well-define hardware/software interface
• The "Contract" between software and hardware

A Language Analogy(유사점) for ISAs

• ISA is analogous to a human language
  • Allows communication (hardware to software)
  • Need to speak the same language
• Key differences : ISAs must be unambiguous

RISC vs CISC Foreshadowing(예고)

• Recall performance equation
  • (instructions/program) (cycles/instruction) (seconds/cycle)
• CISC (Complex Instruction Set Computing)
  • Improve “instructions/program” with “complex” instructions
  • Easy for assembly-level programmers, good code density
• RISC (Reduced Instruction Set Computing)
  • Improve “cycles/instruction” with many single-cycle instructions
  • Increases “instruction/program” , but hopefully not as much
  • Perhaps improve clock cycle time (seconds/cycle)

Good ISA

• Programmability
• Implement-ability
• Compatibility

Assembly Language vs. Machine Language

• Assembly provides convenient symbolic representation
• Machine language is the underlying reality
• Assembly can provide 'Pseudoinstructions'

MIPS Instruction Formats

• 32 bits wide
• very structured, no unnecessary baggage
• three instruction formats