Reminder item: Logic units

Adder: used to add two 32-bit numbers together

Arithmetic Logic Unit (ALU): used for all arithemtic operations (subtraction, addition, etc.)

Multiplexor (MUX): select one of 2 (or more) values to use

From textbook page 246

CPU design diagrams

Note: For final exam, need to be able to read and understand CPU design schematics/diagrams like those in the above images.

Datapath:

• Hardware that performs actual work
• Circuitry that helps with instruction execution in CPU
• e.g., ALU, etc.
• Marked by black lines in above diagrams

Control circuitry:

• Configures datapath for instruction that CPU needs to execute
  • Disables unnecessary components, enables useful components, etc.
• Marked by blue lines in above diagrams

CPU components

Instruction memory component:

• Stores instruction being executed
• Asks for 4-byte instruction from RAM, at the address that it got from the program counter