• Factors affecting performance of the CPU

Question 1

How is memory divided?

Answer 1

• Memory is divided into equal units called words.

Question 2

What is the typical length of words?

Answer 2

8, 16, 32, or 64 bits

Question 3

Where are words stored?

Answer 3

Each word has a separate memory address.

Question 4

What affects the maximum possible memory addresses of the system?

Answer 4

Width of the address bus.

Question 5

What defines the width of the data bus?

Answer 5

Width of the data bus is defined by the number of wires or lines it contains.

Question 6

What determines the format of a machine code instruction?

Answer 6

• Word Size

* Width of the address bus

Question 7

What does the maximum size of an operand depend?

Answer 7

Width of the address bus

Question 8

What factors affect processor performance?

Answer 8

• Clock Speed
• Number of cores in the processor
• Amount & Type of cache memory

Question 9

What is the purpose of the system clock?

Answer 9

• Generates a series of signals, switching between 0 and 1 millions of times per second, and synchronising CPU operations.

Question 10

How do CPU operations depend on the system clock?

Answer 10

• Each CPU operation starts as the clock changes from 0 to 1.
• The CPU cannot perform operations faster than the clock cycle.

Question 11

How is performance affected by the system clock speed?

Answer 11

• All processor activities begin on a clock pulse.

* The greater the clock speed, the faster the computer can fetch, decode and execute instructions.

Question 12

How are operations of the processor synchronised?

Answer 12

• By the system clock, a series of ON/OFF signals are generated and used to synchronise operations.
• Actions are usually carried out on the rising edge of the clock, actions each take a fixed number of cycles to complete.

Question 13

How does the number of cores affect the processor speed?

Answer 13

• Each core is theoretically able to process a different instruction at the same time with its own fetch-execute cycle.
• A greater number of cores can make the computer many times faster, a quad core computer can be four times faster than a single core computer.

Question 14

What is drawback to multiple cores?

Answer 14

• Software may not always be able to take full advantage of multiple cores, meaning a multi core computer will not always perform faster.

Question 15

What is parallel processing?

Answer 15

Using several processor cores working at the same time.

Question 16

How does parallel processing increase performance?

Answer 16

• In systems designed for parallel processing, each core can work concurrently on different parts of the same task.

Question 17

What is a drawback to parallel processing?

Answer 17

• Instructions are processed sequentially, this means that parallel processing is not always possible.

Question 18

What is cache?

Answer 18

• A small amount of expensive, very fast memory inside the CPU, which stores data and instructions that have been recently used by the processor.

Question 19

What is the difference between level 1 and level 2 cache memory?

Answer 19

• Level 1 cache is extremely fast but small

* Level 2 cache is fairly fast and medium sized.

Question 20

What is level 1 cache?

Answer 20

Extremely fast but small sized cache

Question 21

What is level 2 cache?

Answer 21

Fairly fast, and medium sized cache.

Question 22

How is cache memory split, and why?

Answer 22

• Level 1 cache memory is split into instruction cache, and data cache.
• This is to allow data and instructions to be fetched simultaneously

Question 23

How does cache memory affect processor performance?

Answer 23

• The more cache memory a computer has, the more likely it is that it will not have to fetch the next instruction or data to from RAM, as it will have already been loaded into the super-fast cache memory from which it can be retrieved much more quickly.