1.1.1b - performance of the CPU (y12)

Question 2

What is clock speed?

Answer 2

Number of cycles a CPU can execute per second, measured in Hz.

Question 3

How does clock speed affect performance?

Answer 3

Higher clock speed = more instructions executed per second.

Question 4

What is a core in a CPU?

Answer 4

A processing unit capable of executing instructions independently.

Question 5

How does multi-core processing improve performance?

Answer 5

Multiple instructions can be executed in parallel.

Question 6

Why might multi-core not always result in linear speed increase?

Answer 6

Software must be optimised for multi-core usage.

Question 7

What is cache memory?

Answer 7

Small, fast memory inside or near the CPU that stores frequently accessed data.

Question 8

Why is cache important for performance?

Answer 8

Reduces the time needed to access data from main memory.

Question 9

What happens if cache is too small?

Answer 9

CPU has to access slower main memory more often.

Question 10

What are the levels of cache?

Answer 10

L1 (fastest, smallest), L2, and L3 (slowest, largest).

Question 11

Why is RAM slower than cache?

Answer 11

RAM is further from the CPU and not optimised for speed.

Question 12

What does RAM stand for?

Answer 12

Random Access Memory.

Question 13

What is the impact of RAM size on performance?

Answer 13

More RAM = more programs/data held in memory = less disk swapping.

Question 14

What is the purpose of virtual memory?

Answer 14

To use part of the hard drive as RAM when physical RAM is full.

Question 15

What is the downside of virtual memory?

Answer 15

It is much slower than RAM.

Question 16

What is pipelining?

Answer 16

Technique of overlapping fetch, decode, execute cycles for faster processing.

Question 17

What does FDE cycle stand for?

Answer 17

Fetch–Decode–Execute cycle.

Question 18

How can pipelining improve performance?

Answer 18

Increases throughput by allowing multiple instructions in different stages.

Question 19

What is the control unit responsible for?

Answer 19

Directs operations of the processor.

Question 20

What is the role of the ALU?

Answer 20

Performs arithmetic and logic operations.

Question 21

What is the accumulator?

Answer 21

Register that stores intermediate arithmetic/logic results.

Question 22

What does the program counter do?

Answer 22

Holds the address of the next instruction to execute.

Question 23

What is the role of the MAR?

Answer 23

Memory Address Register stores memory location to access.

Question 24

What does the MDR do?

Answer 24

Memory Data Register holds data read/written from memory.

Question 25

What does the CIR hold?

Answer 25

Current Instruction Register stores the instruction being decoded/executed.

Question 26

Why does a CPU need registers?

Answer 26

They provide ultra-fast storage for instruction processing.

Question 27

What is the bus system in a CPU?

Answer 27

Pathways for data/instruction transfer between components.

Question 28

Name the three main buses.

Answer 28

Data bus, Address bus, Control bus.

Question 29

What is the address bus?

Answer 29

Carries memory addresses from CPU to RAM.

Question 30

What is the data bus?

Answer 30

Carries actual data between CPU and memory.

Question 31

What is the control bus?

Answer 31

Sends control signals between components.

Question 32

What factors affect CPU performance?

Answer 32

Clock speed, number of cores, cache size, RAM size, pipelining.