1.1 Systems Architecture

Question 1

What is the Program Counter

Answer 1

Holds the address of the next instruction to be executed and adds one each time so that it points to the next instruction

Question 2

Fixed program machine

Answer 2

Has one purpose - eg. calculator

Question 3

Stored program machine

Answer 3

Has changeable programs

Question 4

What is the Accumulator (Acc)

Answer 4

a special purpose memory location that holds the results of any calculations performed by the arithmetic logic unit (ALU)

Question 5

What is the Memory Data Register (MDR)

Answer 5

Holds data or a program instruction temporarily when it is fetched from memory or data that is waiting to be written to memory

Question 6

What is the Memory Address Register (MAR)

Answer 6

Holds the address (location in memory) of where the data is to be fetched from and then where it is to be stored

Question 7

How is instruction data and program data stored in the computer

Answer 7

In Binary form

Question 8

What is the Random Access Memory (RAM)

Answer 8

The main memory of the computer. Acts as storage for programs and data while the programs are being executed

Question 9

What does the ALU do?

Answer 9

It does the arithmetic calculations & logic and shift operations

Question 10

What are buses

Answer 10

They are the wires that carry all the data around

Question 11

What is a cache

Answer 11

Temporary storage that provides fast access to frequently used instructions and data. It is used to avoid taking extra time going all the way to RAM

Question 12

What are registers

Answer 12

A superfast memory location within the CPU, used in the execution of instructions

Question 13

What three things can affect the performance of the CPU?

Answer 13

• Clock speed
• Cache size
• Number of cores

Question 14

What is a gigahertz? (GHz)

Answer 14

1 billion cycles per second

Question 15

How does clock speed affect the CPU?

Answer 15

Clock speed is the number of instruction cycles that a CPU can do per second so a faster clock speed means a faster CPU

Question 16

How does cache size affect the CPU?

Answer 16

There are three cache sizes:-
Fastest - Can hold the least amount of data - most expensive
Slower - can hold more data
Slowest - Can hold the most data at a time - least expensive

Question 17

How does the number of cores affect the CPU?

Answer 17

The more cores there are, the faster the computer can work. This is because parallel processing can take place with more than one instruction being executes simultaneously. However, double the core does not equal double the speed.

Question 18

What is a core

Answer 18

A complete copy of the CPU each with its own components (ALU, Acc, etc).

Question 19

What is a quad-core processor

Answer 19

a processor with 4 cores

Question 20

What is an embedded system

Answer 20

An embedded system is a computer system with a dedicated or single function and is usually found within a larger mechanical or electrical system. It often has a very basic or no user interface.

Question 21

what is a register

Answer 21

a very fast memory location within the CPU used in the execution of instructions

Question 22

What is the purpose of the CPU

Answer 22

It fetches, decodes, and executes instructions & manages the rest of the hardware

Question 23

What happens in the Fetch-Decode-Execute cycle

Answer 23

FETCH
- The Program Counter is loaded with the location of the next instruction to be executed.

- This address is then loaded into the Memory address register (MAR) which is connected directly to the address bus. What this means is that the address bus is now pointing to the instruction in RAM     The Pc is then incremented by one so that it holds the address of the next instruction to be executed
- This instruction is copied from RAM on to the data bus which then allows the Memory Data Register (MDR) to store a copy of it.

DECODE
The purpose of the decode phase is to look at the content of the MDR and work out if it is a relevant instruction that the CPU can carry out.
• Check to see if the MDR contains a valid CPU instruction - if it does, load the instruction register with the instruction. If it is not valid, then ideally an error is flagged so that the program can deal with it.

EXECUTE

• actually carrying out the instruction present in the instruction register.
• results of processing are held in the accumulator

Question 24

What does the Control Unit do?

Answer 24

Coordinates all the activities inside the CPU and regulates and controls processor timing

Question 25

What is Clock Speed

Answer 25

The speed at which a processor operates. Measured in Hertz (cycles per second).

Question 26

Main Characteristics of an Embedded system

Answer 26

• Program which controls the equipment can’t be changed
• Has a very limited operating system
• Very simple to no user interface

Question 27

Common CPU compoents

Answer 27

ALU
CU
Cache
Registers

Question 28

What is Von Neumann architecture

Answer 28

the design upon which many general purpose computers are based

Question 29

A processor based on Von Neumann architecture has which five special registers

Answer 29

• Program counter
• MAR
• MDR
• Accumulator
  (- CIR)

Question 30

Examples of embedded systems

Answer 30

• central heating systems
• engine management systems in vehicles
• domestic appliances, such as dishwashers, TVs and digital phones
• digital watches
• electronic calculators
• GPS systems
• fitness trackers

Question 31

computer A has a 3.2 GHz processor
computer B has a 1.2 GHz processor

explain why computer A will usually run faster than computer B

Answer 31

• it will have a higher clock speed
• so it will be able to complete more fetch-execute cycles per second
• therefore more instructions can be completed per second