Computer Systems: Chapter 2 (Computer Structure)

Question 1

What are the 3 main parts of the CPU?

Answer 1

• Control Unit
• Arithmetic and Logic Unit (ALU)
• Registers

Question 2

What is the ALU?

Answer 2

The ALU carries out the calculations and performs the logical operations

Question 3

What is the Control Unit?

Answer 3

The Control Unit controls all other parts of the processor and makes sure that the program instructions of the computer are carried out in the correct order

Question 4

What are the Registers?

Answer 4

The Registers are a group of storage locations internal to the processor that hold data being processed, instructions being executed and addresses to be accessed

Question 5

What do the buses do?

Answer 5

They connect the processor to the memory and input/output devices

Question 6

What is the Data bus?

Answer 6

The Data bus carries data to and from the processor to the main memory and any other devices attached to the Data bus, and is bi-directional

Question 7

What is the Address bus?

Answer 7

The Address bus carries the address information from the processor to the main memory and any other devices attached to the Address bus, and is unidirectional

Question 8

What 5 lines is the Control bus made up of?

Answer 8

The Control bus is made up of the read, write, clock, interrupt, and reset lines

Question 9

What is the Read line in the Control bus?

Answer 9

The Read line instructs memory to place data from the specified memory address on the Data bus

Question 10

What is the Write line in the Control bus?

Answer 10

The Write line instructs memory to take data on the data bus and place it in the location specified by the address bus

Question 11

What is the Clock line in the Control bus?

Answer 11

The Clock line carries a series of clock pulses at a constant rate in order to synchronise all operations of the CPU

Question 12

What is the Interrupt line in the Control bus?

Answer 12

The Interrupt line sends a signal to the processor from a peripheral device to stop one routine and give control of the processor to the peripheral device

Question 13

What is the Reset line in the Control bus?

Answer 13

The Reset line returns the processor to its initial state by stopping the current process, saving the contents of the Registers and then resets the system

Question 14

What is the Fetch-Execute cycle?

Answer 14

It is the way in which the processor takes in an instruction from memory (fetch) and carries out that instruction (execute)

Question 15

What are the steps involved in a memory Read operation? (4)

Answer 15

• The processor sets up the Address bus with the required memory address
• The Control Unit activates the read line on the Control bus
• The contents of the particular storage location in memory are released onto the Data bus and copied into the processor’s Memory Data Register.
• If the contents are an instruction then it’s decoded and executed

Question 16

What are the steps involved in a memory Write operation? (4)

Answer 16

• The processor sets up the Address bus with the required memory address by placing a value in the Memory Address Register.
• The processor sets up the Data bus with the value to be written to memory by placing a value in the Memory Data Register.
• The Control Unit activates the write line on the Control bus
• The contents of the Memory Data Register are transferred to the required storage location in the computer’s memory

Question 17

What is Cache memory?

Answer 17

It holds frequently accessed instructions (which speeds up the fetch execute cycle) to speed up system performance

Question 18

What is Main memory?

Answer 18

It consists of a number of storage locations, each with a unique binary address, and is split into RAM and ROM

Question 19

What is Addressability?

Answer 19

It is the method a computer uses to identify storage locations

Question 20

What is a ‘Word’?

Answer 20

A word is the number of bits that can be processed by the processor in a single operation

Question 21

What is Random Access Memory (RAM)?

Answer 21

It is the part of the Main memory that holds its data as long as the computer is switched on

Question 22

What is Read Only Memory (ROM)?

Answer 22

It is the part of Main memory that holds its data even when the computer is switched off

Question 23

How is the maximum capacity of Memory calculated?

Answer 23

(2^width of address bus) x width of data bus in bytes

Question 24

What is the order, from fastest to slowest, of the types of memory?

Answer 24

Registers are the fastest, then Cache, then Main Memory, then Backing storage is the slowest

Question 25

What is Clock speed?

Answer 25

It is the rate at which the Clock generates pulses

Question 26

What is MIPS?

Answer 26

Millions of Instructions Per Second is a measure of the performance of a computer system

Question 27

What is FLOPS?

Answer 27

Floating Point Operations Per Second is another measure of the performance of a computer system

Question 28

What are Application-Based tests?

Answer 28

They are tests which show how a computer system is likely to perform when it is being used to carry out ordinary tasks

Question 29

Why does increasing Data bus width increase computer performance?

Answer 29

It will increase the number of bits that can be transferred in parallel to and from memory

Question 30

What effect does the use of Cache memory have on computer performance?

Answer 30

It will mean that the CPU can quickly get instructions and data from Cache memory, instead of accessing the slower Main memory

Question 31

Why does increasing the rate of data transfer to and from peripherals increase computer performance?

Answer 31

All peripherals operate at slower speeds than the processor, so increasing the rate of data transfer between them will reduce the gap and increase performance

Question 32

What are 3 trends in computer hardware?

Answer 32

• Increasing Clock Speeds
• Increasing Memory
• Increasing Backing Storage Capacity

Question 33

What is an advantage of using MIPS?

Answer 33

MIPS measures processor throughput and are independent of other computer components ie hard disk speed

Question 34

What are the differences between Cache memory and Main memory? (2)

Answer 34

• Cache memory is more expensive per megabyte

* Cache memory has faster access

Question 35

What would be the effect of adding one new line to the address bus on the maximum addressable memory?

Answer 35

The addressable memory size would double

Question 36

Why is using Clock speed alone not an effective way to measure computer performance ?

Answer 36

Clock Speed does not take other important architectural features into consideration (such as data bus width)

Question 37

Why is FLOPS a better measure of system performance that MIPS? (2)

Answer 37

• FLOPS results may be more reliable as logic and arithmetic operations measured are more complex, so would better reflect system performance
• MIPS test may have been performed with small and simple machine instructions, which do not reflect system performance

Question 38

Why do computers not come with the maximum addressable memory installed?

Answer 38

Most programs do not require maximum RAM to be installed