1.1.1 - Architecture of the CPU

Question 1

What is the purpose of a CPU?

Answer 1

A Central Processing Unit (aka processor) has the purpose of fetch, decode and execute instructions.

Question 2

What happens at each stage of the Fetch-Decode-Execute cycle?

Answer 2

Fetch - Instruction is fetched from main memory (RAM)
Decode - Instruction is decoded, to figure out what needs to be done.
Execute - Instruction is performed and carried out.

Question 3

What does the CPU consist of?

Answer 3

Control Unit (CU),
Cache,
Arithmetic Logic Unit (ALU),
Registers.

Question 4

Arithmetic Logic Unit (ALU)

Answer 4

Responsible for carrying out arithmetic calculations and making logical decisions.

Question 5

Control Unit (CU)

Answer 5

Sends signals to control how much data moves around the CPU.

Question 6

Cache

Answer 6

Small of very fast memory which provides fast access to frequently used data and instructions.

Question 7

Registers

Answer 7

Tiny, super fast pieces of onboard memory inside the CPU, where each has a very specific purpose.

Question 9

What are the 4 main registers in the Von Neumann architecture?

Answer 9

MAR (Memory Address Register),
MDR (Memory Data Register),
Program Counter (PC),
Accumulator.

Question 10

MAR (Memory Address Register)

Answer 10

Holds the address of where data is to be fetched or stored.

Question 11

MDR (Memory Data Register)

Answer 11

Holds any data fetched from memory, or is about to be written to memory.

Question 12

Program Counter (PC)

Answer 12

Holds the address of the next instruction in memory.

Question 13

Accumulator (ACC)

Answer 13

Holds the result of calculations.