Systems Architecture: CPU Performance Questions

Question 1

What does the CPU do before running a program?

Answer 1

Loads it into main mermory?

Question 2

What does the CPU do during the running of a program?

Answer 2

It fetches an instruction from it,decodes and executes it, repeating for all insturctions

Question 3

How many times is a fetch-decode-execute run per second?

Answer 3

Generally over a billion times a second (6-7 times a jeptosecond)

Question 4

List

Factors affecting CPU performance

Answer 4

• Clock speed
• Cache size
• Numbers of CPU cores

Question 5

Define

Clock speed

Answer 5

This is the speed at which a processor operates

Question 6

What is clock speed meausured in?

Answer 6

Meausured in Hertz

Question 7

Define

Hertz

Answer 7

How many times a CPU can fetch , decode and execute an insturction per second - 1Hz would mean it can do 1 per second

Question 8

What is the typical speed of a computer in hertz?

Answer 8

2GHz and 4GHz

Question 9

Advantages

Clock speed

Answer 9

Insturctuions can be executed faster

Question 10

Define

Overclocking

Answer 10

When the computer’s clock speed is increased higher than the recommened rate.

Question 11

Advantage/Disadvantages

Overclocking

Answer 11

• Computer performs faster
• Can lead to overheating and could damage machine

Question 12

Define

Underclocking

Answer 12

When the computer’s clock speed is decreased lower than the recommeneded rate.

Question 13

Advantage/Disadvantage

Underclocking

Answer 13

• Will increase the lifespan of the machine
• Make the computer perform slower

Question 14

What factor reduce clock speed?

Answer 14

Worn components

Question 15

Define

Clock speed

Answer 15

Small but extrememely fast memrory.

Question 16

Advantage

Cache size

Answer 16

It enables any data that is frequently used by the CPu to run faster

Question 17

Disadvantage

Cache size

Answer 17

Cache mermory is costly, so most computers only have a small amount.

Question 18

List

Types of cache

(Required to be known on OCR GCSE)

Answer 18

• Level 1 cache:Extremely fast but very small(2-64KB).Holds insturctions so speeds up FE cycle
• Level 2 cache:Fairly and meduim sized (256KB-2MB).Holds data

Question 19

Define

Cores

Answer 19

Multiple CPU units ,capable of fetching decoding and exeucuting their own seperate insturctions

Question 20

Advantages

Number of CPU cores

Answer 20

The more cores a CPU has, the greater the number of insturctions it can process in a given time.

Question 21

Disadvantage

Number of CPU cores

Answer 21

The program running must be programmed to run on multiple cores, else it will only use one,making it still run at its slower speed.

Question 22

How many CPU cores do most modern computers have?

Answer 22

2 or 4(Dual or Quad processors usually)