Chapter 3.1 (A) CPU, Architecture, Cache/Cores

Question 1

What does CPU stand for

Answer 1

Central Processing Unit

Question 2

What components does the CPU consist of

Answer 2

Control Unit (CU)
Arithmetic and logic unit (ALU)
Registers
Busses

Question 3

What does the CPU do

Answer 3

execution or processing of all the instructions and data in a computer

Question 4

What is the Von Neumann architecture

Answer 4

A type of computer architecture which introduced the concept of stored programs in 1940s

Question 5

What is an ALU

Answer 5

The component of the CPU that carries out all arithmetic and logical operations

Question 6

Examples of arithmetic operations that are carried out by ALU

Answer 6

+, -, logical shifting ( multiplication and division)

Question 7

Examples of LOGIC operations that are carried out by ALU

Answer 7

AND and OR

Question 8

What is a register

Answer 8

A temporary component in the CPU which can be
general or specific in its use; it holds data or instructions as part of the Fetch–Decode–Execute cycle

Question 9

Types of special purpose registers

Answer 9

Current Instruction register - CIR
Accumulator - ACC
Memory Address Register - MAR
Memory Data Register - MDR
Program counter - PC

Question 10

What is an ACC (register)

Answer 10

Accumulator - Temporary stores the results of the calculation from the ALU

Question 11

What is a PC (register)

Answer 11

Program Counter - This register stores the address where the next instruction to be read can be found

Question 12

What is the MAR

Answer 12

Memory Address Register - Stores the address of the memory location currently being read from or written to

Question 13

What is the MDR

Answer 13

Memory Data Register - Stores data which has just been read from memory or data which is about to be written to memory

Question 14

What is the CIR

Answer 14

Current information register - this register stores the current instruction being decoded and executed

Question 15

How does the MDR differ from the MAR

Answer 15

The MAR stores the location of the data/instruction

The MDR actually holds the data/instruction itself.

Question 16

Flow of registers

Answer 16

PC –> MAR –> MDR

Question 17

What is the Control unit

what does it decode

Answer 17

CU - Sends control signals that manage the transfer of data and instructions within the CPU. Decodes an instruction using an instruction set

Question 18

What is a bus
what does each wire do

Answer 18

Busses are used in computers as parallel transmission components; each wire in the bus transmits one bit of data

Question 19

3 main types of busses

Answer 19

Address
Control
Data

Question 20

Which busses have two way flow

Answer 20

Control
Data

Question 21

What does the address bus do
direction

Answer 21

Carries addresses throughout the computer system

Unidirectional between CPU and memory

Question 22

How does width of a bus affect the bus (address)

Answer 22

Wider the bus the more memory locations can be directly addressed at any given time.

Question 23

What is a memory location

Answer 23

a numbered place in memory where values can be stored

Question 24

What is an address

Answer 24

a label for a memory location used by the CPU to track data

Question 25

What is a data bus

Answer 25

the system bus that allows data to be carried from CPU to memory (and vice versa) or to and from input/output devices

Question 26

What is a word

Answer 26

a group of bits used by a computer to represent a single unit

Question 27

How does width affect data bus

Answer 27

Wider the bus, the larger word can be transported

Question 28

What is the control bus

Answer 28

the system bus that carries signals from control unit to all other computer components

Question 29

What is the FDE

Answer 29

Fetch-decode-execute cycle - a cycle in which instructions and data are fetched from memory, decoded and finally executed

Question 30

What happens in the fetch stage

Answer 30

Next instruction is fetched from the memory address stored in the MAR and the instructions which are stored at that address are then temporarily stored in the MDR. Then the contents of MDR are copied to CIR. Finally PC is incremented by 1 so that next instruction can be processed

Question 31

What is the decode stage

Answer 31

Instruction is decoded so it can be interpreted in the next part of the cycle

Question 32

What is the execute stage

Answer 32

Instruction carried out in a logical sequence since the CPU passes the decoded instructions as a set of control signals to the appropriate components within the computer system.

Question 33

What is the system clock

Answer 33

produces timing signals on the control bus to ensure synchronisation takes place

Question 34

What is the clock cycle

Answer 34

vibrational frequency of the system clock which sends out pulses along the control bus

Question 35

How is clock cycle measured

Answer 35

Gigahertz GHz

Question 36

What is overclocking

Answer 36

changing the clock speed of a system clock to a value higher than the factory/recommended setting

Question 37

What is the BIOS

Answer 37

Basic Input/Output system - suite of programs on firmware that are used to initialize a computer system during the boot up process.

Question 38

What is cache memory

Answer 38

Temporary memory hold instructions that are freq repeated.

Question 39

Examples of backing store memory

Answer 39

HDD SSD

Question 40

What is a core

Answer 40

a unit on a CPU made up of an ALU, control unit and registers

Question 41

Names and number of cores of CPUs

Answer 41

Dual core - 2 cores Quad core - 4 cores

Question 42

How to increase the speed and performance of a computer

Answer 42

Increasing the bus width (data and address) Increasing the clock speed The use of cache memory Use of multicore CPUs

Question 43

Problems with overclocking

Answer 43

unsynchronised operations which would lead to frequent crashes and the computer becoming unstable Serious overheating of the CPU - unreliable performance

Question 44

Why does increasing the number of cores not always lead to an increase in performance

Answer 44

The CPU needs to communicate with a larger number of cores which could reduce overall performance

Question 45

Explain concept of stored programs

Answer 45

Data and instructions are stored in the same memory and can only be fetched one at a time

Question 46

Purpose of 1 core

Answer 46

to process an instruction to carry out a fetch-execute cycle

Question 47

How can upgrade to dual core impact comp from single core

Answer 47

It can now process two instructions simultaneously (where suitable) * … increasing the performance.