OCR Computer Science - CPU

What is a register?

A small amount of high-speed storage for temporary data.

Give the steps of the FDE cycle

• Fetch - The PC is incremented and the data from RAM with the address from the MAR is fetched and stored in MDR

• Decode - The CU decodes the data

• Execute - The instruction is executed

What is the PC?

The Program Counter stores the address of the next instruction to be executed

What is the MAR?

The Memory Address Register stores the address of the current instruction that needs to be accessed by the CPU.

What is the MDR?

The Memory Data Register stores the instruction retrieved from RAM.

What is the ACC?

The Accumulator stores the results of any calculations made by the ALU (Arithmetic Logic Unit)

How does the CU direct the operations of the CPU?

It sends out control signals

What is Von Neumann architecture?

A computer architecture in which both data and program instructions are stored in the same memory in binary.

What are the four key components of Von Neumann architecture?

• The CPU

• Memory

• INPUT/OUTPUT

• Buses

What is cache?

Temporary storage for frequently accessed data, allowing quicker retrieval by the CPU

How does increasing cache size benefit performance?

Because repeatedly used instructions can be stored and accessed faster.

Why do most computers only have a small amount of cache?

Cache is very expensive

What is clock speed?

How quickly the CPU can perform an instruction

How does clock speed improve performance?

The higher the clock speed the faster the CPU can run the FDE cycle and process instructions, improving performance.