Characteristics Of CPU

Question 1

Function of Control Unit

Answer 1

Coordinates activity between components and decode instructions.

Question 2

Function of the Arithmetic Logic Unit

Answer 2

Responsible for logic and arithmetic calculations (+ - / *), logic, and shift operations.

Question 3

What does the data bus do

Answer 3

Transmits data between instructions.

Question 4

What does the address bus do

Answer 4

Carries the location of the address, where data is going from/to.

Question 5

What does the control bus do

Answer 5

Transmits control signals e.g memory read/write/interrupts.

Question 6

What does the Program Counter do?

Answer 6

Store memory address of the next instruction.

Question 7

What does the Memory Address Register do?

Answer 7

Holds the address being read/written from.

Question 8

What does the Memory Data Register do?

Answer 8

Holds the data that’s being read/written to/from.

Question 9

What does the current Instruction Register do?

Answer 9

Holds the current instruction, decode into op-code and operand

Question 10

What does the accumulator do?

Answer 10

General purpose register stores result from the ALU.

Question 11

Explain the Fetch-Phase in the fetch-execute cycle.

Answer 11

1) Content is the PC are copies into MAR.
2) Memory is read to initiate a copy of the instruction word from memory to the MBR
3) The PC incremented, contains address to next instruction.
4) The instruction word is copied from the MBR into CIR. Instructions contain two parts: opcode and operand.

Question 12

What is the op-code?

Answer 12

Instruction

Question 13

What is the operand?

Answer 13

To perform the operation on.

Question 14

Explain what happens in the Execute-Phase?

Answer 14

1) The opcode instruction in the CIR is decoded into simple operations such as ADD, STORE, and COMPARE.
2) The instructions in the CIR is executed; if the result needs to be committed by memory the address is held in the MAR
3) Unless instructions is stop the cycle is repeated

Question 15

What are the factors that affect performance

Answer 15

1) Multiple Cores
2) Cache Memory
3) Clock Speed
4) Bus width, words

Question 16

What is Pipelining

Answer 16

Completing the fetch-execute cycle in three separate phases instructions simultaneously.

Question 17

What is the stored programme concept

Answer 17

1) Programs needs to be held in main memory to help executed in a processor
2) The instructions is fetched at a time decoded and executed sequentially
3) The sequence of instructions can be changed by a conditional or unconditional jump in instructions

Question 18

Von Neumann Architecture

Answer 18

• Instructions and data are stored in a common main memory and transferred by a single bus.

• Cheaper to develop as control unit is easier to design.
• Programs can be optimised in size
• Good for general purpose.

Question 19

Harvard Architecture

Answer 19

• Program and dats and stored in separate main memory and transferred by two separate buses.

• Quicker execution as data and instructions can be fetched in parallel
• Memories can be different sizes which can make efficient use of space.
• Hardware connections expensive: have two buses.
• Harvard principles can be used with specialist embedded systems.

Question 20

Contemporary Processing

Answer 20

• Combination of Von Neumann architecture and Harvard
• Von Neumann used when working with data and instructions in main memory Harvard Architecture to divide cache into instruction cache and data cache.

Question 21

Assembly Language

Answer 21

• Assembly code uses mnemoics to represent instructions: it’s a simplified way of writing machine code
• The instructions is divided into operand and op-code in Current Instruction Register.

Question 22

RISC

Answer 22

• Reduced Instruction Set Computers
• Have a small instruction set.
• Each instruction is one line of machine code and takes one clock cycle.

Question 23

CISC

Answer 23

• Complex Instruction Set Computers
• Have a large instruction set.
• Used in microcontrollers and embedded systems.

Question 24

RISC vs CISC

Answer 24

RISC
- The complier has to do more work translating high level code into machine code
- More RAM required to store the code.
- Pipelining possible since each instruction takes one clock cycle.

CISC
- The complier can do less work then translating high level code into machine code.
- Less RAM is required since the code is shorter
- Many specialized instructions are made in only a few of them are used.

Question 25

Multicore processor

Answer 25

able to distribute workload across multiple processors units, thus achieving significantly higher performance by performing several tasks in parallel

Question 26

Co-processors.

Answer 26

extra processor used to supplement the functions of the primary processor

• **maybe used in floating point arithmetic, graphics processing digital signal processing and other functions
• carries out only a limited range of functions

Question 27

GPU

Answer 27

• Graphics Processing Units is a specialised electronic circuit which is very efficient at manipulating computer graphics and image processing
• Consists of thousand of small efficient cores designed for parallel processing
• Can process large blocks of visual data simultaneously

Question 28

Function of GPU

Answer 28

• A GPU can act together with CPU to accelerate scientific, engineering, and other applications

Question 29

What does RAM stand for

Answer 29

Read only Memory

Question 30

What does ROM stand for

Answer 30

Read only memory

Question 31

Features of RAM

Answer 31

Stores: Operating system, running programs, and data currently being used

Volatile - memory is erased when computer has no power

It can be read and written to

Question 32

Features of ROM

Answer 32

Stores: Computing bootup instructions (bootstrap), BIOS.

Non-volatile - retain memory when there’s no power to the computer

read-only.

Question 33

What is virtual memory

Answer 33

Part of the hard drive used as an extension to RAM

Question 34

How does virtual memory work

Answer 34

• Applications or programs are loaded and coped into the RAM from secondary storage, so RAM starts to fill up.
• You want to load another program but there’s no space.
• The part of the hard drive is used as RAM and the programme is stored there.

Virtual storage is slower as reading and writing from RAM is much more faster