1.1.1 - The CPU

Question 1

What are the registers in the CPU? (5)

Answer 1

PC, ACC, MAR, MDR, CIR

Question 2

What does the PC hold? (1)

Answer 2

The location of the next instruction to be fetched (1)

Question 3

What is a register? (2)

Answer 3

A small piece of memory used for storing data (1) within the processor (1)

Question 4

State two features of the Von Neumann Architecture (2)

Answer 4

Single control unit (1) single ALU (1) registers within the CPU (1) Instructions and data stored in same area of memory (1) a single set of buses connect CPU and memory (1)

Question 5

What is the cycle the Von Neumann Architecture completes? (1)

Answer 5

Fetch decode execute (1)

Question 6

What is the difference between CISC and RISC? (4)

Answer 6

Cisc has more complex circuitry so is more expensive to make (1) RISC has simpler circuitry making it cheaper to make (1) Each RISC instruction takes one clock cycle (1) CISC instructions may take more than one clock cycle (1)

Question 7

What are the three factors that affect the performance of a CPU? (3)

Answer 7

Clock speed (1) number of cores (1) amount of cache memory (1)

Question 8

Explain two differences between RAM and ROM (4)

Answer 8

RAM is volatile (1) used for storing open programs and data. (1) ROM is non volatile (1) used for storing BIOS (1)

Question 9

What are the key features of GPUs? (2)

Answer 9

Specialised in processing graphics (1) Tasks are multiprocessed using a large number of cores. (1)

Question 10

What is the role of the ALU? (2)

Answer 10

Processes arithmetic (1) and logic (1) in the CPU.

Question 11

What is the role of the control unit? (3)

Answer 11

It sends control signals to coordinate the movement of data through the processor (1) controls buses (1) decodes instructions (1)

Question 12

What is the role of the accumulator? (1)

Answer 12

Holds data that the CPU is currently working on (1)

Question 13

What is the role of the MAR? (4)

Answer 13

Contains the address of the instruction to be accessed in memory (1) it recieves this from the PC (1) or it can contain the address of the data to be accessed in memory (1) and sends it to the CIR (1)

Question 14

What is the role of the MDR? (3)

Answer 14

Contains the instruction or data that has been accessed from memory (1). Sends that instrution to the CIR. (1) Acts as a buffer. (1)

Question 15

What are the three buses used by the CPU? (3)

Answer 15

Control (1) Address (1) Data (1)

Question 16

What is the role of the control bus? (1)

Answer 16

Transmits control signals from the control unit to the rest of the computer (1)

Question 17

What is the role of the Address bus? (1)

Answer 17

Carries the address where data is moving to or from. (1)

Question 18

What is the role of the Data bus? (1)

Answer 18

Carries data (1)

Question 19

What happens during the fetch stage of the FDE cycle? (7)

Answer 19

Address of next instruction copied from PC to MAR (1) PC is incremented by 1 (1) Data in MAR is passed to address bus (1) Read signal is sent on the control bus (1) RAM copies the data specified by the address bus to the data bus (1) Data on the data bus is passed to the MDR (1) Data on the MDR is passed to the CIR (1)

Question 20

What is pipelining? (3)

Answer 20

Concurrent processing of multiple instructions (1) one instruction can be fetched while the previous is being decoded (1) and the one before that is being executed (1) In the case of a branch the pipeline is flushed (1)

Question 21

Why does pipelining increase processor speed? (2)

Answer 21

All parts of the processor can be used at any instance in time (1) parts of the CPU are not idle while waiting for the next instruction (1)

Question 22

What are the key features of the Harvard Architecture? (3)

Answer 22

Separate memory stores for instructions and data (1) separate buses for memory and data (1) instructions and data can be stored on different hardware (1)

Question 23

Give two uses of the accumulator. (2)

Answer 23

Temporary storage (1) for data being processed (1) Stores input / output in processor (1) can be used as a buffer (1)

Question 24

Give one non-graphical use for a GPU (2)

Answer 24

Performing complex numerical calculations (1) eg calculations on matrices / vectors / large data sets (1)