Components Of A Computer

Question 1

What does the control unit do?

Answer 1

Controls and coordinates what the CPU is doing. Directs the flow of data between CPU and other devices. It accepts the next instruction, decodes it into several steps and manages its execution.

Question 2

What is a bus?

Answer 2

A bus is a set of parallel wires connecting two or more components of a computer.

Question 3

What are the three buses the CPU is connected to?

Answer 3

address, data and control

Question 4

How does the CPU use the address bus?

Answer 4

When the CPU wants to access a location in the main memory, it sends the address to the memory along the address bus.

Question 5

How is the data bus used?

Answer 5

Data retrieved from the main memory is returned to the CPU on the data bus

Question 6

What is the ALU?

Answer 6

Arithmetic Logic Unit. Performs arithmetic and logical operations.

Question 7

Name the five registers in the CPU

Answer 7

Program Counter
Current Instruction Register
Memory Address Register
Memory Data Register
Accumulator

Not the ALU idiot

Question 8

What is the PC used for?

Answer 8

Holds the address of the next instruction to be executed.

Question 9

What is the CIR used for?

Answer 9

Holds the current instruction being executed, divided into operand and opcode

Question 10

What is the MAR used for?

Answer 10

Holds the address of the memory location where data is being retrieved/written to

Question 11

What is the MDR used for?

Answer 11

Used to temporarily store the data read from or being written to memory.

Question 12

Describe the fetch phase of the Fetch-execute cycle

Answer 12

The address of the next instruction is copied from the PC to the MAR.
The contents of the MAR are sent along the address bus to main memory.
The data held at that address in memory is returned along the data bus and copied to the MDR. Simultaneously the content of the PC is incremented.
The contents of the MDR are copied to the CIR.

Question 13

Describe the decode phase of the fetch-execute cycle

Answer 13

The instruction in the CIR is passed to the decode unit to be decoded by splitting it into the opcode and operand.
The decoded address is stored in the MAR.
It goes along the address bus to the address in the main memory. The data there is passed along the data bus and stored in the MDR and is then sent to the ALU where it is executed.

Question 14

What is the accumulator used for?

Answer 14

Used to save the result of operations carried out in the ALU.

Question 15

What is pipelining?

Answer 15

As the current instruction is being executed in the ALU, the next instruction is being fetched from memory.

Question 16

What is von Neumann architecture?

Answer 16

Data and instructions are together in memory. The same data bus is used to transfer both data and instructions from main memory and a single address bus is used.

Question 17

What is the stored program concept?

Answer 17

machine code instructions are fetched and executed serially by a processor that performs arithmetic and logical operations.

Question 18

What is Harvard architecture?

Answer 18

When instructions and data are stored in two different memories. This allows for parallel data and instruction buses to be used.

Question 19

What is CISC?

Answer 19

Complex Instruction Set Computers. Complex instructions are built into the machine’s hardware, which means less lines of code have to be written in the assembly program.

Question 20

What is RISC?

Answer 20

Reduced Instruction Set Computer. Only simple instructions that take one clock cycle are available.

Question 21

What are the advantages of CISC? (3 things)

Answer 21

The compiler has to do less work to translate high level languages into machine code.
The instructions are short, so they take up less space in RAM.
Programmers writing in assembly have to write less code

Question 22

What are the disadvantages of CISC?(3 things)

Answer 22

Many specialised instructions are built into the hardware that are rarely used.
Processors require more circuitry and so are more expensive to make
Processors use more power as they contain more components such as capacitors.

Question 23

What are the disadvantages of RISC? (3 things)

Answer 23

The compiler has to do more work to translate high level languages into machine code.
The instructions are large, so they take up more space in RAM.
Programmers writing in assembly have to write more code.

Question 24

What are the advantages of RISC?(2 things)

Answer 24

All instructions take the same time, so pipelining is possible.
Processors have less circuitry so they are cheaper to make.

Question 25

What is a co-processor?

Answer 25

An extra processor used to supplement the functions of the primary processor. It may be specialised at performing a certain task, such as handling graphics.

Question 26

What are the advantages of a multi-core system?

Answer 26

Allows you to process one set of instructions faster by splitting the workload between different cores.
Allows you to run multiple programs at one time.

Question 27

What does a GPU do?

Answer 27

A GPU handles computer graphics and image rendering. It is very efficient at doing repetitive tasks, such as updating the pixels on a monitor.

Question 28

What is the structure of a GPU?

Answer 28

A GPU is made up of thousands of small cores connected in a parallel architecture.

Question 29

Name 4 factors that affect the performance of a CPU

Answer 29

Clock speed
Number of cores
Cache memory size
If pipelining is being used

Question 30

What is contemporary architecture?

Answer 30

Contemporary processors use a combination of Harvard and Von Neumann architecture.
Von Neumann is used when working with data and instructions in main memory, but uses Harvard architecture for the cache.