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Computer Science > Unit 1 - System architecture > Flashcards

Unit 1 - System architecture Flashcards

1
Q

What is the purpose of the CPU?

Architecture of CPU

Mark scheme answer

A

Processes instructions.
It is the part of the computer that fetches and executes the instructions that are stored in memory.
The CPU contains the Arithmetic Logic Unit (ALU) and the Control Unit (CU).

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2
Q

How is the CPU different to the brain?

Architecture of CPU

A
  • CPU simply runs one simple instruction at a time
  • It carries out billions of instructions per second
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3
Q

What is the Von-neumann architecture?

Architecture of CPU

A

Program instructions and the data the programs are using are both stored in the same memory
The CPU accesses both instructions and data from the same RAM

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4
Q

What are the 2 main components of CPU?

Architecture of CPU

A
  • Control Unit
  • Arithmetic Logic Unit
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5
Q

What are registers?

Architecture of CPU

A

A register is a very fast
memory location in the
CPU itself

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6
Q

What is cache?

Architecture of CPU

Mark scheme answer

A

Cache stores frequently used instructions/data
that can be accessed faster than accessing them from RAM

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7
Q

What are the registers in the CPU?

Architecture of CPU

A
  • Program Counter
  • Memory address register
  • Memory data register
  • Accumulator
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8
Q

What does the PC do?

Architecture of CPU

Mark scheme answer

A

Stores the address of the next instruction to be fetched from memory.
Increments in each fetch-execute cycle.

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9
Q

What does the MAR do?

Architecture of CPU

Mark scheme answer

A

Stores the address of the data to be fetched from, or the address where the data is to be stored.

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10
Q

What does the MDR do?

Architecture of CPU

A

holds the actual instruction, and then the data that has been fetched from memory

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11
Q

What does the accumulator do?

Architecture of CPU

A

holds the result of an instruction before it is transferred to memory

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12
Q

What is the function of te CU?

Architecture of CPU

Mark scheme answer

A

Coordinates the processor and F-E cycle
Decodes instructions
Runs F-E cycle

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13
Q

How does the CU control the CPU?

Architecture of CPU

A
  • It decodes instructions and executes them
  • It receives signals from the system clock
  • It directs the timing and control of other parts of the CPU
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14
Q

What does the ALU do?

Architecture of CPU

A

ALU is where the actual arithmetic operations are done and also carries out logical operations

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15
Q

How do the MAR and MDR work in the F-E cycle?

Architecture of CPU

A
  • CU decodes the instruction and decides if data needs to be fetched
  • address of the instruction to be executed is copied from PC to MAR
  • instruction at that address is fetched from memory and copied to MDR
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16
Q

How does the CPU operate?

Architecture of CPU

FDE cycle

A

The CPU operates by repeating three operations:
- FETCH – causes the next instruction and any data involved to be fetched from main memory
- DECODE – decodes the instruction
- EXECUTE – the instruction is executed

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17
Q

What affects the performance of CPU?

CPU performance

A
  • Clock speed
  • Processor cores
  • Cache
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18
Q

How does clock speed affect performance?

CPU performance

A
  • Everything in a computer happens on the pulse of the internal clock
  • Therefore, the faster the clock speed, the faster the instructions are processed per second
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19
Q

How do multicore processors affect performance?

CPU performance

Mark scheme answer

A

Dual core is double the number of processors. Parallel processing can take place which means each processor can execute a separate instruction at the same time which enables multitasking
Some processes/software cannot be
split between two processors so it does not increase the performance

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20
Q

What is cache memory?

CPU performance

A

Cache is a very small amount of memory that is between the CPU registers and RAM. When an instruction is fetched from main memory it is copied into the cache so if it is needed again soon after, it can be fetched from cache which is much quicker than going back to main memory. As cache fills up, unused instructions or data still being held are replaced with more recent ones.

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21
Q

How does cache affect perfromance?

CPU performance

Mark scheme answer

A

Cache stores frequently used data that can be accessed faster than
accessing them from RAM
So more cache improves the performance of the CPU.

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22
Q

What is an embedded system?

CPU performance

Mark scheme answer

A

Embedded system has specific function. And has a microprocessor on a single circuit board

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23
Q

What are the 2 types of primary storage?

Memory

A
  • RAM
  • ROM
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24
Q

What is RAM?

Memory

A

The computer stores running programs and data in RAM when your computer is turned on
When your computer is turned off, data store in RAM is lost

25
Q

What does RAM store?

Memory

A
  • The operating system (or part currently in use)
  • The software currently in use
  • The data which the software is using
26
Q

What is virtual memory

Memory

A

Virtual memory is part of the hard drive used as an extension to RAM

27
Q

How does virtual memory work?

Memory

Mark scheme answer

A

VM is used when RAM is full, part of the secondary storage used as temporary
RAM. Data from RAM is moved to the VM (to make space in RAM). RAM can then be filled with new data. When data in VM is needed it is moved back to RAM

28
Q

What are the advantages of vitual memory?

Memory

A
  • Uses cheap secondary storage on the hard drive
  • Prevents error messages saying ‘out of memory’ – the programs and files will still open
29
Q

What are the disadvantages of virtual memory?

Memory

Mark scheme answer

A
  • Excessive use can cause disk thrashing decreasing performance
  • VM is slower to access than RAM direct
  • Moving data between RAM and VM takes processor time
30
Q

What is ROM?

Memory

A
  • Some data needs to be permanently held in primary storage, even when a computer has no power
  • Data is read from ROM, but cannot be written to it
  • It is non-volatile as the data isn’t lost if the power is off
31
Q

What does ROM store?

Memory

A

The initial program that is run when the computer is turned on (bootstrap)
It tells the computer where it will find the operating system on the hard drive
It also stores the BIOS

32
Q
A
33
Q

What is secondary storage?

Secondary storage

A

It is non-volatile, meaning it will keep data even if there is no power. Secondary storage devices may be internal or external to the computer.

34
Q

What is secondary storage
used for?

Secondary storage

A
  • Programs + data stored on hard drive
  • Blu-rays to distribute films
  • Memory sticks to transport data from one place to another
  • Magnetic tape or external hard drives may be used for backup
  • SD cards can be used for additional storage on cameras and smartphones – this is used for music, video and photos
35
Q

What are 2 types of secondary stroage?

Secondary storage

A
  • Solid state drive
  • Hard disk drive
36
Q

What are 3 storage methods?

Secondary storage

A
  • magnetic
  • optical
  • solid state
37
Q

How does magnetic disk work?

Secondary storage

A

Disk contains concentric circles called tracks. Each track is divided into sectors. Disk heads mounted on mechanical arms read and write the data

38
Q

What are advantages of magnetic storage?

Secondary storage

A

Cheap, large storage capacities, relatively fast write speed

39
Q

What are disadvantages of magnetic storage?

Secondary storage

A

Lots of mechanical parts, durability an issue, sealed unit due to disk head and platter precision and not very portable

40
Q

What are uses of magnetic storage?

Secondary storage

A

Personal computers, storage of large quantities of data

41
Q

What is a magnetic device’s capacity?

Secondary storage

A

500GB - 12TB or greater

42
Q

How does optical storage work?

Secondary storage

A

Data is stored as pits and lands burnt or pressed into a spiral track circulating outwards from the centre. A laser beam passes over the pits and lands the level of reflection is measured. From this signal, 0s and 1s can be derived

43
Q

What are advantages of optical storage?

Secondary storage

A

Cheap, very easily portable, takes up little space physically

44
Q

What are disadvantages of optical storage?

Secondary storage

A
  • Less storage capacity compared to other types
  • Easily damaged / scratched, requires a CD reader
  • Slow write speeds
45
Q

What are uses of optical sotrage?

Secondary storage

A

Songs, videos and other multi-media storage, backup and archiving of data

46
Q

What is the capacity of optical storage?

Secondary storage

A

CD-ROM – up to 720 MB
DVD – up to 8.4 GB (dual layered disk)
Blu-Ray – up to 50 GB (dual layered disk)

47
Q

How does a SSD work?

Secondary storage

A
  • Solid-state disks use non-volatile flash memory to store information
  • Very fast read/write speeds as it doesn’t need to wait for a disk to spin to the correct location and an arm to move
  • No mechanical or moving parts meaning these disks are very durable
48
Q

How does flash memory work?

Secondary storage

A

Large electric current used to force electrons through a barrier and trap them on the other side. They remain on the other side until ‘flashed’ with a new current, hence the name
Trapped (charged) or not trapped = 0 or 1

49
Q

What are advantages of SSD?

Secondary storage

A

Highly durable, no moving parts, very fast read/write speeds, no noisy fan or drive arm, faster start up times

50
Q

What are disadvantages of SSD?

Secondary storage

A

More expensive than magnetic hard disks, similar storage capacity as magnetic disks

51
Q

What are uses of SSD?

Secondary storage

A

Higher end computers
Laptops
Smartphones and tablets

52
Q

What is SSD’s capacity

Secondary storage

A

100GB – 16TB

53
Q

Compare portability of SSD and optcal storage

Secondary storage

A

Both are Small in size / portable and
can easily be moved between Kerry’s
home and work
Solid state can be smaller
Solid state less likely to break

54
Q

Compare robustness of SSD and optcal storage

Secondary storage

A

Optical are not robust i.e. easily
scratched/damaged while being moved
Solid state has no moving parts so
unlikely to break if dropped

55
Q

Compare cost of SSD and optcal storage

Secondary storage

A

Optical cost is small per GB
Solid state can be reused more times
because it’s more durable so may be
cost effective in the long term

56
Q

Describe what the internal secondary storage device will store

Secondary storage

A

Software / applications / program including OS
files

57
Q

State benefits of SSD instead of magnetic

Secondary storage

A

faster access/read/write speed
Smaller in physical size // more
compact // weighs less
More durable/robust
Uses less power
Runs cooler
Quieter when running

58
Q

State drawbacks of SSD instead of magnetic

Secondary storage

A

limited number of read/write times
more expensive (per byte)
(usually) smaller capacity

Computer Science (7 decks)

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