1.1 Systems Architecture

Question 1

Computer

Answer 1

An electronic device which takes an input, decodes and outputs a set of instructions given by the user.

Question 2

Purpose of the CPU

Answer 2

To fetch, decode and execute instructions.

Question 3

What is the FDE Cycle

Answer 3

A repetitive cycle where the CPU fetches, decodes and executes instructions given by the user.

Question 4

Events that take place during the FDE Cycle

Answer 4

• The CPU receives an instruction from memory.
• The CPU decodes the instruction.
• The decoded instruction is executed.
• The PC is incremented.
• The process is repeated.

Question 5

CPU Components

Answer 5

• Arithmetic Logic Unit (ALU)
• Control Unit (CU)
• Cache
• Registers

Question 6

ALU

Answer 6

Responsible for carrying out all arithmetic calculations and making logical decisions.

Question 7

CU

Answer 7

Sends signals to control how data moves around the CPU.

Question 8

Cache

Answer 8

Provides fast access to data and instructions that are used frequently.

Question 9

CPU Registers

Answer 9

• Program Counter (PC)
• Memory Address Register (MAR)
• Memory Data Register (MDR)
• Accumulator (ACC)

Question 10

What are registers?

Answer 10

Tiny, superfast pieces of onboard memory inside the CPU.

Question 11

PC

Answer 11

Holds the address of the next instruction in memory.

Question 12

MAR

Answer 12

Holds the address of where data is to be fetched or stored.

Question 13

MDR

Answer 13

Holds the data fetched from, or to be written to memory

Question 14

ACC

Answer 14

Holds the results of calculations performed in the CPU

Question 15

Von Neumann Architecture

Answer 15

Processor architecture that stores both instruction data and program data in the same memory in binary form.
There is no way to know if the pure binary represents instructions or data.

Question 16

Characteristic of Von Neumann Architecture

Answer 16

• CPU
• Single Control Unit
• ALU
• Onboard cache
• Internal clock
• Memory unit (typically RAM)

Question 17

Factors Affecting CPU Performance

Answer 17

• Clock Speed
• Cache size
• Number of cores

Question 18

What is Clock speed?

Answer 18

Number of FDE cycles per second that the CPU can perform, measured in Hz.

3.2Ghz = 3.2bil instructions fetched per second.

Question 19

What is Cache?

Answer 19

Small amount of memory that is closer to the CPU than RAM. Used to temporarily hold instructions and data that the CPU is likely to reuse.

Question 20

What is a core?

Answer 20

A complete copy of a CPU.

Question 21

Effect of Clock Speed on CPU Performance

Answer 21

The higher the clock speed, the more instructions that the CPU can execute per second, increasing the overall speed of the computer.

Question 22

Effect of Cache Size on CPU Performance

Answer 22

The greater the cache size, more data and instructions can be fetched more quickly, as it is closer than RAM.

Question 23

Effect of Number of Cores on CPU Performance

Answer 23

The more cores a computer has, the faster it can process instructions as it has multiple CPUs.

Question 24

Disadvantages of multiple cores

Answer 24

• Doubling the number of cores doesn’t necessarily double overall speed as the cores have to communicate with each other, which takes time.
• Many programs aren’t designed for multiple cores.

Question 25

Embedded System

Answer 25

A computer system with a dedicated function within a larger mechanical system

Question 26

Properties of Embedded Systems

Answer 26

• Low power consumption
• Small size
• Rugged operating systems
• Low cost per unit

Question 27

Examples of Embedded Systems

Answer 27

• Dishwasher
• Washing machine
• GPS systems
• Dryer
• Medical devices eg. pacemaker or insulin pump