Structure + function of a processor Flashcards

1
Q

What is the CPU

A

Central Processing Unit - Runs programs by continuously fetching, decoding and executing instructions

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2
Q

What is the ALU

A

Arithmetic Logic Unit - Carries out the calculations and logical decisions.

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3
Q

What is the CU

A

Control Unit
- Sends out signals to co-ordinate how the processor works
- It controls how data moves around parts of the CPU and memory
- Instructions are decoded in the control unit

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4
Q

What is a register

A

A discrete piece of memory built onto the CPU that holds a single piece of data

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5
Q

What is the PC

A

Program Counter - Keeps track of the location of the line of machine code being executed

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6
Q

What is the MDR

A

Memory Data Register - Stores the data or instructions that are to be fetched from memory or sent to memory

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7
Q

What is the MAR

A

Memory Address Register - Stores the address of the data or instructions that are to be fetched from memory or sent to memory

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8
Q

What is the CIR

A

Current Instruction Register - Stores the most recently fetched instruction, which will be decoded and executed

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9
Q

What is the ACC

A

Accumulator - Stores the results of calculations made by the ALU

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10
Q

What are buses

A

The communications channels through which data can be sent around the computer

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11
Q

What is the purpose of the data bus

A

Carries data between the processor and memory

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12
Q

What is the purpose of the address bus

A

Carries the address of the memory location being read from or written to

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13
Q

What is the purpose of the control bus

A

Sends control signals from the control unit

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14
Q

Describe what happens when fetching instructions

A
  • Contents of the PC are copied to the MAR
  • The read signal is sent across the control bus and the contents of the MAR are sent across the address bus
  • The contents of the memory location stored in the MAR are then sent across the data bus and stored in the MDR
  • The contents of the MDR are then copied to the CIR
  • The PC is incremented by one
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15
Q

Describe what happens when decoding instructions

A
  • The contents of the CIR are sent to the CU
  • The CU then decodes the instruction
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16
Q

Describe what happens when executing instructions

A

If the instruction is…
- for a memory location to be read from or written then the address stored within the instruction will be loaded into the MAR
- to carry out a calculation then the contents of the MDR and ACC are sent to the ALU and the results are sent back to the ACC

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17
Q

What is the clock speed

A

The frequency at which the clock generator of a processor can generate pulses

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18
Q

What is a core

A

A processing unit within the CPU

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19
Q

How does clock speed affect performance

A

Higher clock speed, the faster the CPU can run and the more instructions that can be processed every second

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20
Q

How does the number of cores affect performance

A

More cores, easier it is to run more things simultaneously. This means tasks that can share their work will run faster

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21
Q

What is cache

A

A fast memory that is built on or close to the CPU and is designed to reduce the need to access RAM which has slower access speeds

22
Q

How does cache improve performance

A

Faster to access data than RAM

23
Q

What is pipelining

A

Different parts of the CPU performing different parts of the fetch-decode-execute cycle on a sequence of instructions

24
Q

Disadvantage of pipelining

A

If there is a branch instruction then the CPU has to try predict the next instruction to keep the pipeline full. If it gets it wrong then the pipelines have to get flushed and performance is degraded

25
Q

What is a computer architecture

A

The approach taken in a computer’s design

26
Q

What does Von Neumann architecture contain

A
  • a single control unit
  • a single arithmetic logic unit
  • a single memory store that contains both instruction and data
27
Q

What does Harvard architecture have

A
  • a single control unit
  • a single ALU
  • a memory unit for data
  • a bus for data
  • a memory unit for instructions
  • a bus for instructions
28
Q

What is a thread

A

A sequence of instructions sent to the CPU to be processed

29
Q

What is simultaneous multithreading

A

Allows two threads to run on each core at one time

30
Q

What is ‘out of order execution’

A

Allows instructions to be executed ahead of when they usually would be if the required resources are needed, preventing delay.

31
Q

What is RISC

A

Reduced Instruction Set Computing - A design approach where a CPU uses a small set of instructions

32
Q

What is CISC

A

Complex Instruction Set Computing - Processors with a large instruction set with more complex instructions

33
Q

What is a GPU

A

Graphics Processing Unit - Designed to perform the calculations associated with displaying graphics

34
Q

Features of GPUs

A
  • Instruction set specifically designed for graphics processing
  • Can process pieces of data in parallel
35
Q

Where can GPUs be used in apart from graphics

A
  • Modelling physical systems
  • Audio processing
  • Breaking passwords
  • Machine learning
36
Q

What is parallel processing

A

When a computer carries out multiple computations simultaneously to solve a given problem

37
Q

What is SIMD

A

Single Instruction Multiple Data - The same operation is carried out on multiple pieces of data, at one time

38
Q

What is MIMD

A

Multiple Instructions Multiple Data - Different instruction are carried out concurrently on different pieces of data

39
Q

What is hardware

A

Physical components of a computer system

40
Q

What is meant by ‘peripheral’

A

Hardware attached to and used with a computer, but are not an integral part of it

41
Q

What is magnetic storage and examples

A

Patterns of magnetisation are used to represent binary sequences.
e.g Hard disk drive, Magnetic tape

42
Q

What is optical storage and examples

A

Uses a laser and by looking at its reflection, determines where there are pits on a surface, which represent binary.
e.g CD, DVD, Blu-ray

43
Q

What is flash storage and examples

A

Uses a special type of read-only memory that can be overwritten
e.g USB, SD card and SSD

44
Q

What is RAM

A

Random Access Memory - A type of primary memory that the CPU uses for programs and data in use. It loses its contents when power is loss

45
Q

What is ROM

A

Read Only Memory - A type of primary memory that can only be read from. It retains its contents even when electrical power is lost. It’s often used to store start-up instructions on a computer

46
Q

What is ROM often used for

A

The computer’s boot program/ BIOS

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