1. CPUz 4 n00bz

2. CPU Diagram Program Cache Counter (PC) RAM (Memory) Instruction
Control Unit (CU)
Program
Counter (PC)
Cache
Address Bus
Instruction
Register (IR)
Decoder
Arithmetic Logic Unit (ALU)
Data Bus
Accumulator

3. Additional CPU Components
Program counter (PC)
Holds the address of the next instruction in the program sequence
Instruction register
Holds the operation code of the type of instruction to be executed (e.g. ADD, SUB)
Accumulator
ALU’s internal register that holds ongoing total

4. Fetch-Execute Again
Fetch instruction from the address stored in the program counter
Store instruction in instruction register
Decode instruction register
Execute operation (control unit tells ALU what to do)
ALU performs operation and uses its accumulator to remember result
Store accumulator result back to memory

5. What happens when we need to pause the fetch-execute cycle?
Interrupts!
Things that “interrupt” the processor’s normal operation
Handle events and exceptions
Keyboard input
Null pointer exception
etc.
Special code exists to handle instructions, which is also stored in RAM

6. Interrupt Register
Stores the offset address of the special interrupt handling code
Interrupt Code Address = Base Address + Interrupt Register
Basically…it stores the location in memory of where you go to handle the interrupt

7. Processor Optimizations
Pipelining
Fetch-execute cycle overlapping for multiple instructions

8. Instruction Pipelining

9. More Cool Optimizations
Multiprocessing
Dual-core and Quad-core processors
Cell processor has 8 processors!