lecture4.pptx

CISC/RISC

CISC

• Reducing register file size
  • Transistor cost was high
• Reduces program size (memory expensive)
• Complex instructions
  • Simplify assembly programming

RISC

• Smaller set of instructions
• Optimized to be in single clock
• Identical general purpose registers
• Simple address mode
• Fewer data types
• Fixed-length instructions

Motivations:

• Often faster
• Memory got cheaper faster
• Transistors cheaper
• Complier was better

How did Intel “convert” from CISC to RISC?

Microcoding CISC instructions into many RISC instructions