Computer Architecture

Question 1

What is the definition of a computer system?

Answer 1

A computer system takes a set of digital inputs, processes them and creates a set of outputs. This is done by a combination of hardware and software.

Question 2

How does data get into a computer system?

Answer 2

The data gets into a computer system by using an ‘input device’, such as a keyboard.

Question 3

List three examples of input devices which can be used to input data.

Answer 3

Keyboard
Microphone
Mouse

Question 4

What is another name he CPU might be known by?

Answer 4

Microprocessor.

Question 5

Explain the role of a program within a computer system?

Answer 5

A computer program, otherwise known as software, provides the CPU with a set of instructions to perform a specific task. The instructions are carried out in the CPU.

Question 6

Give an example of software which might provide instructions.

Answer 6

Systems software such as the operating system.

Applications software such as a music player or word processing application.

Question 7

What is meant by output, giving reference to output devices?

Answer 7

After data has been processed it will normally by output, which provides the processed data in a format that the user can understand and use. In order to output the data you need an output device, for example if the output is music then headphones or speakers would be an appropriate output device.

Question 8

Explain why processed data is sometimes stored rather than output.

Answer 8

The processed data might be part of a larger task and the CPU needs to store it until the rest of the data is ready to be used all together.

Question 9

Explain the role of the data bus within a computer system.

Answer 9

A data bus is a set of wires or tracks laid down on a printed circuit board. A data bus carries the data around the computer system, for example from the input device to the CPU to the output device. Each wire or track carries a single bit.

Question 10

Explain what is meant by an embedded computer and give an example?

Answer 10

An embedded computer is one that is part of a larger piece of equipment and is usually out of sight. For example, it would be part of a smart TV washing machine or car.

Question 11

State the main role of the CPU.

Answer 11

The CPU fetches instructions from memory, it decodes the instructions and then executes those instructions. It processes data using the instructions.

Question 12

List three examples of hardware the CPU might control.

Answer 12

Hard Disk
DVD Drive
Sound System

Question 13

State were the CPU is located within a computer.

Answer 13

On the motherboard under the heat sink and cooling fan.

Question 14

Name the three main parts found within a CPU.

Answer 14

Control Unit
Arithmetic Logic Unit
Registers

Question 15

What is used to carry data within the CPU and also to and from main memory?

Answer 15

Data Buses

Question 16

Identify three tasks that the Control Unit performs.

Answer 16

It controls the way data moves around the CPU. (Main Task)
It controls and monitors the flow of data between the CPU and other components, such as input devices, memory, graphic card etc.
It executes the instructions provided by the program

Question 17

Identify the two tasks the ALU performs.

Answer 17

Arithmetic operation - It performs standard arithmetic operations such as addition, subtraction, multiplication etc.
Logical operation - It deals with the logic and comparisons such as ‘is this value greater than that value?’ the answer is always either ‘true’ or ‘false’.

Question 18

Briefly explain the role of a register within the CPU.

Answer 18

Registers are used to hold temporary data while a software program is running. As the CPU processes the data, the software program will shift the data in and out of the registers.

Question 19

State the purpose of the cache.

Answer 19

The cache is a small, but extremely fast type of RAM. It can help speed up processing time.

Question 20

Explain why there is a clock inside the CPU.

Answer 20

The clock is a small quartz crystal which ‘ticks’ at a steady speed. During each ‘tick’ the CPU can process a single instruction.

Question 21

Outline the function of the clock inside the CPU.

Answer 21

The clock inside the CPU ‘ticks’ at a regular speed. Each time it ticks, the CPU can process a single instruction.

Question 22

Identify why there is an upper limit at which the CPU clock can comfortably run.

Answer 22

As the clock ticks it generates power and this heats up the CPU chip. If the clock speed is too high, the temperature of it would increase too much and the CPU could get burned out.

Question 23

Explain what is meant by overclocking and identify why people might want to overclock their CPU.

Answer 23

If you want to overclock your CPU, you increase the frequency at which the clock ‘ticks’ at. Overclocking your CPU can help make your computer faster as more instructions can be processed each second. Meaning the CPU can run faster than its normal design speed. People may want to overclock their CPU, if they are keen gamers, to make their game faster. (This can be useful playing video games which require intense processing).

Question 24

A CPU has been overclocked. Identify how it is possible to do this without permanently damaging the CPU chip.

Answer 24

It is possible if you improve the cooling system to cool down the CPU. For example a water-cooled computer or a computer cooled by liquid nitrogen.

Question 25

What is meant by the term ‘core’.

Answer 25

A core is a complete processing unit within the CPU - it contains an ALU, CU and registers.

Question 26

Outline how increasing the number of cores can lead to an improvement in the CPU’s performance.

Answer 26

Each core can process a single task when the clock ticks. If there are 2 cores then two tasks can be processed each tick of the clock. If there are 4 cores then four tasks can be processed simultaneously, therefore extra cores means that more tasks can be processed at the same time.

Question 27

What is meant by multi tasking?

Answer 27

Multi tasking is the ability to carry out more than one task at the same time. For this more than one core is required. Clearly, with two cores, a CPU can run two tasks simultaneously.

Question 28

What is meant by parallel processing?

Answer 28

Parallel processing is when a single task is split into two or more parts and each part is processed at the same time.

Question 29

Why won’t parallel processing necessarily lead to an improvement in CPU performance?

Answer 29

Because many programs can’t be split neatly into two independent parts. This is because they are mostly sequential (each task depends on the outcome of the previous task so it has to wait for the first task to be completed).

Question 30

Outline the role of the cache.

Answer 30

It’s a small temporary store for frequently used instructions.

Question 31

Identify why having a larger cache can speed up processing time.

Answer 31

Having a larger cache will speed up processing time because the CPU can access data and instructions faster than they can from RAM. If frequently used instructions or data are stored in cache, the CPU doesn’t have to fetch them directly from RAM. And with a larger cache, more instructions or data can be stored there, resulting in a faster processing time.

Question 32

Why is there usually a limit to how much cache memory is used in a computer system?

Answer 32

The more cache included in the computer system, the more expensive the computer system.

Question 33

What is the purpose of RAM in a computer system?

Answer 33

RAM is the main memory that is used to store computer programs and data that are currently in use.

Question 34

What is the purpose of virtual memory?

Answer 34

Virtual memory is an area set aside on the hard disk to act as a very slow form of RAM. It is used to store some of the currently running programs and data if RAM is full.

Question 35

Why will your computer appear to be running slow if it doesn’t have sufficient RAM?

Answer 35

If RAM is full virtual memory would have to be used. As virtual memory is an area of the hard drive, it would be slower to access. If the virtual memory is in heavy use, the computer will seem to be running very slowly.

Question 36

If too much RAM is added you are unlikely to see a further improvement in performance. Explain why this might happen.

Answer 36

If too much RAM is added there isn’t a further improvement in performance as there is lots of excess RAM which isn’t being used, as there is more RAM than memory required by all of the other programs to run the applications.

Question 37

If you are running a video game, explain how installing a graphics card could help improve the performance of your system.

Answer 37

The graphics card contains a graphics processing unit which is designed to handle graphics and images much faster than the CPU. Therefore after installing a graphics card, the CPU will send any graphics related tasks directly to the GPU while it continues to process other tasks, therefore the performance of your system would improve as graphics files are large and often require much processing.

Question 38

Name some issues that you might need to consider when thinking about installing a graphics card to improve performance.

Answer 38

They’re expensive.
They only improve performance on graphics or video files.
They use a lot of power, therefore the computer would need to be fitted with a more powerful power supply.
Because they use a lot of power, they need a cooling fan, which are noisy.

Question 39

What is meant by Von Neumann architecture?

Answer 39

Von Neumann architecture is where both the data and the software that are currently being used are stored in computer memory (RAM).

Question 40

Give another name for Von Neumann architecture.

Answer 40

A stored program computer.

Question 41

Give the features of the Von Neumann architecture.

Answer 41

There is a CU responsible for handling the movement of instructions and data around the computer.
There is a ALU responsible for carrying out calculations and logic comparisons.
Data and instructions are carried on buses.
There needs to be enough memory to hold both programs and data.
There are registers inside the CPU, eg the accumulator.
There is a way to input into the computer and to output information.

Question 42

What is an alternative computer architecture to Von Neumann?

Answer 42

Harvard Architecture.

Question 43

Describe the role of the memory data register.

Answer 43

The MDR temporarily stores data and instructions as they are fetched from RAM, before passing them on to be processed. Data can also be temporarily stored after being processed before being passed back to RAM.

Question 44

Describe the role of the memory address register.

Answer 44

Every piece of data or each instruction has it’s own unique address in RAM. The address of the data or instruction being accessed for processing is temporarily stored in the MAR.

Question 45

Describe the role of the program counter.

Answer 45

As each instruction is processed, the software that is currently running updates the program counter with the address of the next instruction to fetch. The program counter then passes this next address to the MAR as part of the standard fetch/decode/execute cycle.

Question 46

Describe the role of the accumulator.

Answer 46

The accumulator is used to temporarily store data whilst calculations are being performed within the ALU.

Question 47

List the five registers involved with the fetch/decode/execute cycle.

Answer 47

Program counter, memory address register, memory data register, instruction register, accumulator.

Question 48

At the start of the fetch/decode/execute cycle, where will the instruction or data be fetched from?

Answer 48

Main memory (RAM).

Question 49

Only one program can be running in main memory, true or false?

Answer 49

False.

Question 50

Describe what happens during the fetch part of the fetch/decode/execute cycle.

Answer 50

The program counter is updated with the location. The address location is copied to the MAR. The CU loads the address from the MAR onto the address bus. The data is taken from that location in main memory. That data is loaded onto the data bus. The data is stored in the MDR. The instruction in the MDR is copied into the instruction register. The program counter is now incremented by one location.

Question 51

Explain what happens in the decode part of the fetch/decode/execute cycle.

Answer 51

The CU reads the instruction register and makes sure that it’s an instruction that the CPU can carry out. It does this by checking the instruction register against the instruction set. If the instruction is not recognised as valid it may flag an error or crash the program.

Question 52

What happens in the execute part of the fetch/decode/execute cycle.

Answer 52

It may involve making a calculation or a logical comparison, which is handled by the ALU. The results of the calculation may be stored in a register in the CPU, or may be returned to main memory if the program requests it.