Processor Performance

Question 1

What does the width of the address bus determine?

Answer 1

• Width of the address bus determines the maximum possible memory addresses/memory capacity of the system.
• Maximum size of RAM.

Question 2

What does it mean for the data bus to be bi-directional?

Answer 2

Data can be sent both ways along the bus.

Question 3

What is the width of the data bus defined by?

Answer 3

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

Question 4

What does the data bus do?

Answer 4

Data bus transmits the data held in a word of memory, between processor components and memory.

Question 5

How does the width affect the data bus?

Answer 5

• The size of the data bus determines the maximum size of an operand in an instruction.

Question 6

What does the maximum size of the operand depend on?

Answer 6

The maximum size of the operand depends on the width of the address bus.

Question 7

What are the main factors affecting processor performance?

Answer 7

• Clock speed
• Number of cores in the processor
• Amount and type of cache memory.

Question 8

How does the clock speed affect performance?

Answer 8

• The fetch execute cycle is triggered by the clock pulses of the system clock
• Faster the clock speed, the faster a computer can fetch, decode and execute instructions.
• CPU cannot perform operations faster than the clock cycle.

Question 9

What does the system clock do?

Answer 9

Generates a series of signals, switching between 0 and 1, and synchronising CPU operations.

Question 10

how do CPU operations relate to 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 does number of cores affect processor speed?

Answer 11

Each core is able to process a different instruction at the same time, with its own fetch execute cycle, meaning an increase in cores can increase the number of cycles concurrently happening, increasing performance.

Question 12

What is parallel processing/

Answer 12

Using several processor cores working at the same time.

Question 13

How does parallel processing affect the fetch execute decode cycle?

Answer 13

• Each core can concurrently work on different parts of the same task

Question 14

What is a drawback to parallel processing?

Answer 14

Instructions are processed sequentially, parallel processing is therefore not always possible.

Question 15

What is cache?

Answer 15

A small amount of super fast memory that stores data and instructions that have been recently used by the processor.

Question 16

What is cache split into, and how is this advantageous?

Answer 16

• Cache memory is split into instruction and data cache.

* This allows data and instructions to be fetched simultaneously.

Question 17

How does cache memory affect performance?

Answer 17

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

Question 18

What is pipe-lining?

Answer 18

Overlapping stages in the fetch execute cycle, or breaking down the stages in an arithmetic instruction, this is designed to improve performance.

Question 19

What are the different levels of cache?

Answer 19

• Level 1 cache, extremely fast but small.
• Level 2 cache, fairly fast but medium sized.
• Level 3 cache