07 Computer Organsation And Architecture

Question 1

What is a computer system?

Answer 1

Any device that can take a set of inputs and process them into useful outputs

Question 2

What is the CPU and what are its components?

Answer 2

The central processing unit

It is made of the 
Processor
Main memory
Address, control and data buses
Input/Output (I/O) controllers

Question 3

What are I/O controllers?

Answer 3

An interface between the device and the computer

Question 4

What is a device driver?

Answer 4

Software that directly interacts with the I/O controller

It converts signals from the device into a format the computer can process and vice versa
It receives I/O requests from the CPU, and then sends control signals to the device it is controlling
It also manages the data flow to and from the device, freeing the CPU to get on with other tasks

Must be installed when you use a new device

Question 5

What is a bus?

Answer 5

A series of wires that transfer data signals between internal components

Question 6

What is the control bus?

Answer 6

Sends control signals between each I/O controller and the processor as well as between the processor and memory

Control signals include memory read and write and clock

Question 7

What is the data bus?

Answer 7

It is bi directional as data can be sent both ways along it

The width is defined by the number of wires or line it has

It affects system performance

Question 8

What is the address bus?

Answer 8

It carries the address of a memory location in one direction from the processor to I/O controllers and memory

The width of the address bus determines the maximum possible memory addresses of the system

A 32 bit bus can carry 2^32 addresses

Question 9

How is memory divided?

Answer 9

Into equal units called words

Question 10

What is main memory?

Answer 10

It stores data and instruction that are to be processed

Number of memory addresses is constrained by the width of the address bus

The smallest addressable unit is a word

Question 11

What is stored program concept?

Answer 11

When computers are designed to allow data and instructions to be stored in order for it to perform different tasks at different times

Machine code instructions are loaded into main memory to be executed by the processor and they are fetched one at a time to be executed immediately in order

Question 12

What is von Neumann architecture?

Answer 12

Most common implementation of the stored program concept

Instructions and data are stored in a common main memory and transferred using a single shared bus

Question 13

What is Harvard architecture?

Answer 13

The data and instructions are separated into different memories using different buses

Program instructions and data don’t compete for the same bus and may be stored in unequal quantities

Different sized memory spaces and word lengths can be used for data and instructions

Question 14

What is the processor and its components?

Answer 14

It controls, calculates and executes instructions

Arithmetic Logic Unit
Control Unit
Clock 
General Purpose Registers
Dedicated Registers

Question 15

What is the arithmetic logic unit?

Answer 15

The problem solving part of the computer

It performs arithmetic (+ -), logical (AND, NOT) and shift (move bits to left or right) operations on data

Question 16

What is the control unit?

Answer 16

The part of the processor that coordinates the activity of all the other components

Instruction accepted and decoded
Separate steps such as fetching the address of data, and fetching the data itself from memory, are identified
Each step is synchronised with a regular pulse from the system clock

Question 17

What is the system clock?

Answer 17

A series of regular ON/OFF signals that synchronise the operations of the processor components

Question 18

What are general purpose registers?

Answer 18

Locations of super fast memory that temporarily store results from the ALU

Processor can access and reuse this data

Some processors have a single general purpose register called the Accumulator

Question 19

What are dedicated registers?

Answer 19

Program Counter - Holds the memory address of the next instruction

Current Instruction Register - Holds the current instruction

Memory Address Register - Holds the address in memory where the processor is required to fetch or store data from or to

Memory Buffer Register - Temporarily holds data moving between the processor and main memory

Status Register - Holds information about the current state of operations. Used to overflow or detect errors

Question 20

What is the fetch execute cycle?

Answer 20

1. Next instruction which is stored in the program counter is copied to the memory address register. The program counter is then incremented by one.
2. Memory address register sends it to memory using the address bus. The address bus only sends one way.
3. The main memory takes the address and looks at the instructions and sends it to the processor along the two way data bus into the memory buffer register and the memory data register.
4. It is then passed onto the current instruction register. This is the end of the fetch as the data is then decoded and executed
5. The data is split into two parts, the opcode and the operand. The opcode is the operation part (+ - ) and the operand is the thing that the opcode is going to work on.
6. The operation is carried out in the Arithmetic logic unit in the execute part of the cycle. The status register is then updated after every instruction to show flags depending on whether the result is; Negative, positive, overflow, under flow etc.
7. The results of the process is then stored in the accumulator and the cycle returns to step one.

Question 21

What improves processing speed?

Answer 21

Cache - Small amount of super fast memory that is frequently used by the processor (higher cache)

Number of cores - More processor can be linked together on a single chip allowing more instructions to be executed

Address and data bus width

Word length - Amount of data that CPU can process simultaneously

Question 22

What is assembly language?

Answer 22

A code where mnemonics are used to represent the operation codes and addresses

Question 23

What is operation code (opcode) and operand?

Answer 23

Opcode - The actual command the processor needs to carry out

Operand - One or more items of data that are used in the instruction