Computer Architecture

Question 1

What is Von Neumann architecture?

Answer 1

A computer whose programs and data it uses is stored in the same memory

Question 2

Describe the fetch-execute cycle

Answer 2

An instruction is brought from the RAM.
It is then decoded by the CU to find out what to do with the instruction
The instruction is then carried out

Question 3

What is the purpose of the CPU?

Central Processing Unit

Answer 3

To continuously process instructions and data that are inputted by repeatedly carrying-out the FE cycle

Question 4

What is the function of the ALU?

Answer 4

Carries out the mathematical and logical operations (e.g. AND, OR, NOT) and compares values held in registers

Question 5

What is the function of the CU?

Answer 5

• Coordinates all of the CPU’s actions in the FE cycle
• Decodes all instructions
• Sends and receives control signals to fetch and write data

Question 6

What is the function of the clock?

Answer 6

It regulates the speed and timing of all signals and computer functions

Question 7

What are the registers in the CPU?

Answer 7

PC
MAR
MDR
ACC
CIR

Question 8

What is the purpose of the registers?

Answer 8

They are very small, fast memory locations that temporarily store memory addresses, instructions and data

Question 9

What does the CIR do?

Answer 9

Holds the instruction currently being executed

Question 10

What does the MDR do?

Answer 10

Holds data or a program instruction after it is stored/fetched from memory

Question 11

What does the ACC do?

Answer 11

Where the ALU stores its results (from its operations)

Question 12

What is the PC?

Answer 12

Holds the memory address of the next instruction to be executed

Question 13

What are the seven steps in the FE cycle?

Answer 13

1. The memory address held in the PC is copied into the MAR
2. The PC is incremented. It now holds the address of the next instruction
3. The processor sends a signal across the address bus to the memory address held in the MAR
4. The instruction/data held in that memory address is sent along the data bus to the MDR
5. The instruction/data in the MDR is copied into the CIR
6. The instruction/date held in the CIR is decoded and then executed (results held in ACC)
7. The process repeats

Question 14

What three factors affect CPU performance?

Answer 14

Clock speed
Cache size
Number of cores

Question 15

How does clock speed affect CPU performance?

Answer 15

One tick of the clock counts as one FE cycle.
So the faster the clock, the more ticks there are, the more FE cycles there are

Question 16

How does the number of cores affect CPU performance?

Answer 16

• A CPU can contain multiple cores, with each core processing one operation per clock cycle
• A dual/quad-core can perform two/four operations simultaneously therefore more clock cycles

Question 17

Why might a computer with a dual-core not necessarily be faster than a single-cored computer?

Answer 17

If the software used is only written for one core, additional cores may be redundant

Question 18

What is cache memory?

Answer 18

It is a small amount of very fast memory that can be accessed faster than RAM

RAM is further away from the processor than cache

Question 19

What are the benefits of cache?

Answer 19

Makes the CPU more efficient as less time is spent waiting for data to be transferred

Question 20

Which is (theoretically) faster?
1) A dual-core processor running at 3.2GHz with 4MB of cache memory

2) A dual-core processor running at 2.7GHz with 4MB of cache memory

3) A single-core processor running at 3.2GHz with 2MB of cache memory

4) A quad-core processor running at 1.5GHz with 8MB of cache memory

Answer 20

1) 2 x 3.2 GHz = 6.4 GHz + 4MB
2) 2 x 2.7 = 5.4GHz + 4MB
3) 1 x 3.2 GHZ = 3.2GHZ + 2MB
4) 4 x 1.5GHZ = 6GHz + 8MB

Therefore 1 is fastest

But 4 is slightly slower with more cache/cores so it could be faster

Question 21

What is an embedded system?

Answer 21

Used to control the function of electronic devices that don’t need a full OS since they perform specific tasks. Their input is also frequently controlled by a switch/button

Question 22

What are some examples of embedded systems?

Answer 22

Air conditioning, microwaves, vending machines, lighting systems

Question 23

What is an NIC?

Answer 23

Hardware required to be able to access any network

Can be wireless or use an Ethernet cable to connect

Question 24

What is a MAC address?

Answer 24

A unique, hexadecimal, static ID number assigned to every NIC used in network devices

Static = It does not change

Question 25

What is a MAC address format?

Answer 25

12 character (6 byte) hexadecimal address
e.g. 30-A5-BD-6F-CF-63

Question 26

What do the first three bytes of a MAC address tell us?

Answer 26

Makes up the unique manufacturer code
30-A5-BD-6F-CF-63

Question 27

What do the last three bytes of a MAC address tell us?

Answer 27

Makes up the unique serial code of that specific device
30-A5-BD-6F-CF-63

Question 28

What is an IP address?

Answer 28

A static or dynamic address allocated to each device. It can be assigned by a router

Internet Protocol

Question 29

What is a router?

Answer 29

A device for connecting network-connected devices together to form a network

They collect knowledge of available routes to transmit data and then determine the most suitable route for sending data.

Question 30

Where do routers ‘sit’ in a network?

Answer 30

Between local networks and the Internet to join them together with the public IP address from the Internet and the private IP address from the local network

Question 31

What is an ISP?

Answer 31

Assigns the IP address for your network

Internet Service Provider?