Background: Before RISC

Goal: Speed Up Computation

Evolution of computers before RISC

• Gradually build more and more complex functionality into hardware (& machine language).
  • Goal: Make those complex functions faster

Problem: The Clock!        

• Every computer has a clock.
• Acts as a metronome, sending pulses that set the pace of instructions moving through hardware.
• Each instruction happens in one "tick" (basically).
• Design goal: speed up instructions, aka speed up the clock.
• Note: Complex instructions are slower -- limit clock speed-up.
• General goal of computer designers: Speed up computation.

Big Idea: Reduced Instruction Set Computers (RISC)

• Take the most complex instructions out of the hardware / machine language.
• Those instruction now have to be done in software again.
• Speed up the simple instructions that remain; speed up the clock.
• IMPORTANT POINT: Programs have many more simple instructions than complex ones.