4. Computer Components

Question 1

Components of Von Neumann Architecture

Answer 1

Two types of units:
1) Units that process information
2) Units that store information

This units are:
1) Memory Unit

2) Arithmetic/Logic Unit (ALU)

3) Input unit

4) Output Unit

5) Control Unit

Question 2

Bus

Answer 2

Set of wires that connect all major sections of Von Neumann Machine

Role:
transfer data, signals or power between components

Size/jwidth of bus is how many bits it carries in parallel

Question 3

Memory

Answer 3

Collection of cells, each with a unique physical address

Number of bits that the OS operates at determines the number of addresses that can be accessed and the amount that can be stored in each address

Question 4

Arithmetic / Logic Unit (ALU)

Answer 4

Performs basic arithmetic operations

INclude a small amnount of special storage units –> registers

Question 5

Input Unit

Answer 5

Device used to enter external data into computer

Question 6

Output Unit

Answer 6

Device through which results are made available

Question 7

Control Unit

Answer 7

Organizing force in the computer

Components:
1) Instruction register
2) Program Counter

Question 8

Instruction Register (IR)

Answer 8

Contains the instruction that is being executed

Question 9

Program Counter (PC)

Answer 9

Contains the address of the next instruction to be executed#

Increments one by one, to the point of the next instruction to be executed

Question 10

Central Processing Unit (CPU)

Answer 10

ALU + Control Unit

Question 11

Throughput

Answer 11

Measure of how many units of information a system can process in a given amount of time

Question 12

Pros of VN Architecture

Answer 12

Data and instructions to manipulate data are logically the same –> could be stored in the same place

Question 13

Cons of VN Architecture

Answer 13

VN Bottleneck (reasons performance is limited):

-Single data bus can only access one of the two classes of memory at a time

-Data transfer rate is lower than rate that CPU can process (Bottleneck)

Question 14

Fetch-Execute Cycle

Answer 14

1) Fetch next instruction

2) Decode instruction

3) Get data if needed

4) Execute the instruction

5) Store result of execution and check for next instruction

Question 15

Fetch the next instruction

Answer 15

PC –> CU –> IR

Question 16

Decode the instruction

Answer 16

IR –> CU –> CPU

Instruction is decoded into signals –> logic of the circuity in the CPU determines which operation is to be executed

Question 17

Get data

Answer 17

IR –> CU –> additional memory address

Question 18

Execute the instruction

Answer 18

CU –> ALU –> Mescellaneous tasks

Computer can only execute instructions that are in its own ML

Question 19

Cache Memory

Answer 19

Small amount of fast-access memory into which copies of frequently used data are stored

Question 20

Cache Principles

Answer 20

Temporal Locality

Spatial Locality

Aim:

• Store the memory locations that are most likely to be accessed again in expensive, high-speed memory

Question 21

Temporal Locality

Answer 21

Most recently accessed memory locations are more likely to be accessed again in the future

Question 22

Spatial Locality

Answer 22

Most recently accessed blocks of program are more likely to be accessed again than are less recently accessed blocks of a program

Question 23

Main memory

Answer 23

Can be of two categories:

1) Random-Access Memory (RAM)

2) Read-Only Memory (ROM)

Question 24

RAM

Answer 24

Memory in which each location can be accessed and changed

Volatile

Question 25

ROM

Answer 25

Memory in which each location can be accessed but not changed

Not volatile

Stores the instructions that a computer needs to start itself

Question 26

Seek time

Answer 26

Time it takes for read/ write head to be over right track

Question 27

Latency

Answer 27

Time it takes for sector to be in position

Question 28

Access time

Answer 28

Seek time + Latency