The Processor

Question 1

Purpose of the CPU

Answer 1

• To process machine instructions
• Carry out the fetch-decode-execute cycle

Question 2

3 Main components of CPU

Answer 2

CU, ALU, RAM

Question 3

What is the CU?

Answer 3

Control Unit: Sends control signals to other components - responsible for organising the FDE of instructions - controls input/output devices - communicates with all parts of the CPU

Question 4

What is the ALU?

Answer 4

Performs calculations and makes logical decisions

Question 5

What is RAM?

Answer 5

Holds the data and instructions for the currently running programs

Question 6

What are registers?

Answer 6

Stores the programs which are needed instantly e.g. software applications

Question 7

5 registers

Answer 7

1) Accumulator
2) PC
3) CIR
4) MDR
5) MAR

Question 8

Accumulator

Answer 8

Holds the data currently being processed - results of calculations carried out by ALU

Question 9

Program Counter

Answer 9

Holds the memory address of the next instruction to be executed - increments the next instruction to be fetched

Question 10

Current Instruction Register

Answer 10

Stores the address of the instruction currently being executed

Question 11

Memory Data Register

Answer 11

Stores data being transferred temporarily - all data to and from memory must travel down the data bus and pass through the MDR

Question 12

Memory Address Register

Answer 12

Stores the address of the memory location currently in use - sends address to memory down the address bus

Question 13

Address Bus

Answer 13

Carries the address of the memory locations

Question 14

Data Bus

Answer 14

The contents of the instruction are carried

Question 15

Control Bus

Answer 15

Informs whether the info is read or write control signals

Question 16

Bus Width

Answer 16

The number of wires that make up a bus - determines the range of instructions that can be transmitted

Question 17

Fetch Stage

Answer 17

• PC register displays the address in RAM of the next instruction to be processed
• This value is copied into the MAR
• The PC is incremented by 1
• This prepares the CPU for the next instruction to be fetched
• The CPU checks the address in RAM which matches the address held in the MAR
• The instruction in RAM is transferred to the MDR
• The instruction in the MDR is copied into the CIR

Question 18

Decode Stage

Answer 18

The instruction in the CIR is understood and decoded - CU sends signals using the 3 busses

Question 19

Execute Stage

Answer 19

Any result of an execution is stored in the ACC register

Question 20

Clock Speed

Answer 20

How many CPU cycles can be run per second - the bigger the number the more cycles can be run per second

Question 21

Overclocking

Answer 21

Making a computer or component operate faster than the clock frequency specified by the manufacturer - system can become unstable and there is a risk of damage due to excessive heat generation

Question 22

Cache

Answer 22

Cache memory is used as the RAM is significantly slower than the speed CPUs operate - fast memory built into the processor reducing the distance data has to travel to it

Question 23

Cores

Answer 23

Additional processors

Question 24

Increasing the number of cores

Answer 24

Ensures cycles can be run simultaneously

Question 25

Increasing cache size

Answer 25

Ensures more frequently used programs can be accessed much faster

Question 26

Multicore Processor

Answer 26

Single chip containing two or more independent processing units - each core can FDE its own instructions

Question 27

Chip with 2 cores

Answer 27

Dual-core processor

Question 28

Chip with 4 cores

Answer 28

Quad-core processor

Question 29

Limitation of multicore processing

Answer 29

Double the number of cores does not mean double the performance (overheads involved with inter-core communication, some programs cannot make maximum use of all cores

Question 30

Parallel Processing

Answer 30

The processing of program instructions by dividing them between multiple processors or processor cores

Question 31

Limitation of parallel processing

Answer 31

The extent parallel processing can speed up computation depends on the task being carried out and if the software is designed to make use of parallel processing

Question 32

Co-processor

Answer 32

Any additional processor used for a specialised task - improves the overall speed of a computer by executing concurrently

Question 33

Graphical Processing Unit (GPU)

Answer 33

- Run slower than a CPU core - Highly specialised - superior in speed and efficiency for certain tasks - Better than CPUs for larger data sets