System Architecture

Question 1

What is the purpose of CPU?

Answer 1

The processor is “the brains of a Computer System”
It Processes Data
Carries out instructions (Executes Them)
Retrieves Data/Instructions from Main Memory (Fetch)
Processors have a Clock speed measured in Hertz
Number of Cycles Per Second

Question 2

What measurement is used to assess the speed of CPU?

Answer 2

MHz and GHz

Question 3

How many instructions can 1 GHz can execute per second?

Answer 3

1 Billion

Question 4

What is a core in processor?

Answer 4

Core, is where the instructions get processed.

Question 5

Processor can be multi-core, what are the common terms used for these?

Answer 5

Dual core, Quad core, 8 cores

Question 6

What is the advantage of dual core over single core processor?

Answer 6

Dual Core may execute up to twice as many instructions per second

Question 7

What is cache memory?

Answer 7

This is a small memory chip inside the processor.
It acts as an intermediary between the processor and the Main Memory
As programs are executing – the Cache holds commonly used instructions

Question 8

What affects the performance of CPU?

Answer 8

Clock speed, Cores, Cache size

Question 9

What is an embedded system?

Answer 9

A computer System that is made up of both Hardware and Software
Usually for very specialised tasks
Doesn’t usually contain an Operating System
An example: Dishwasher

Question 10

What are the internal components of a computer?

Answer 10

The processor
Main memory
I/O controllers
Buses

Question 11

What are the external components(Peripherals) of a computer?

Answer 11

Keyboards, Mouse, Printer, disk drives
|I/O devices, I/O ports
Secondary Storage

Question 12

What is RAM?

Answer 12

RAM – Random Access Memory
Holds Data and Instructions that are currently in use by the processor
Located on the Motherboard
Directly Accessible by the processor
All data/instructions are lost once power is turned off

Question 13

What is ROM?

Answer 13

ROM – Read Only Memory
Instructions are permanently etched onto a ROM Chip
When power is turned off – instructions still remain on the ROM chip.
Bootstrap Loader is held in ROM
Gives the instructions to start up the Operating System

Question 14

What are I/O controllers?

Answer 14

These are used to allow an interface between a hardware device external to the motherboard (e.g. a Keyboard) and the Processor itself.
I/O controllers are used for:
Keyboard, Mouse, Disk Drive, VDU

Question 15

What are System Busses?

Answer 15

A bus is a set of parallel wires connecting two or more independent components of a computer system in order to pass signals between them.

The System is split into three separate busses:
The data bus
The address bus
The control bus

Question 16

What does address bus do?

Answer 16

Carries addresses from the Processor to main memory or other I/O devices
It is one direction (Uni-Directional)
The processor generates an address
All data/Instructions are returned on the Data Bus

Question 17

What does data bus do?

Answer 17

Carries Data/Instructions from Main Memory to the Processor (or from other secondary storage devices) to the processor.
Bi-Directional (two way)
Data can be read/written

Question 18

What does the control bus do?

Answer 18

Control signals are sent along the control bus
E.g. Memory Read, Memory Write
This instructs which was data will be travelling to/from memory.

Question 19

What are Peripheral devices?

Answer 19

Peripherals are any devices that are not directly connected to the CPU
E.g. mouse, keyboard, printer, hard disk drive, cd-rom drive
These devices are known as I/O devices (Input/Output Devices)

Question 20

What are I/O ports?

Answer 20

I/O Ports allow communication from an I/O device and the motherboard (hence CPU)

Question 21

Process registers:

What does PC-program counter do?

Answer 21

Holds the location of the next instruction/data address in Main Memory

Question 22

What does MAR – Memory Address Register ?

Answer 22

The contents of the PC are copied here and then transferred along the Address Bus

Question 23

What does MDR – Memory Data Register

Answer 23

Once Data/Instructions are brought from the Memory Address in Main Memory – they are placed in the MDR.

Question 24

What does CIR – Current Instruction Register do?

Answer 24

The instructions stored in the MDR are copied here

Question 25

What happen in Fetch, decode and execute cycle?

Answer 25

Decode / Execute Part
The instruction to be decoded is held in the Current Instruction Register
The instruction is split into an Op-Code and an Operand
The instruction is carried out by the ALU (Arithmetic Logic Unit)

Question 26

What is ALU function?

Answer 26

Performs arithmetic and logical operations including +, -, AND, OR

Question 27

What does register Accumulator holds?

Answer 27

Results of calculations are placed into the Accumulator