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OCR A-level Computer Science > 1.1 The characteristics of contemporary processors, input, output and storage devices > Flashcards

1.1 The characteristics of contemporary processors, input, output and storage devices Flashcards

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1
Q

What is a processor?

A

seen as ‘the brain’ of the computer
-executes instructions allowing programs to run

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2
Q

What is the function of the ALU

A

arithmetic and logic unit- completes the arithmetical and logical operations

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3
Q

What is the function of the control unit? Give examples (3)

A

directs operations inside the CPU
-controls and coordinates activities of the CPU
-manages flow of data between CPU and other devices
-decodes instructions

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4
Q

What are registers? What do they do?

A

-small memory cells which operate at very high speeds
-used to temporarily store data such as arithmetic, logical and shift operations

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5
Q

Name all the registers (5)

A

-program counter (PC)
-accumulator (ACC)
-memory address register (MDR)
-memory data register (MAR)
-current instruction register (CIR)

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6
Q

What is the PC used for?

A

program counter (PC) - holds address of the next instruction to be executed

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7
Q

What is the ACC used for?

A

accumulator (ACC) - stores results from calculations

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8
Q

What is the MAR used for?

A

memory address register (MAR) - holds address of a memory location that has been fetched or data that needs to be written

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9
Q

What is the MDR used for?

A

memory data register (MDR)- temporarily stores data that has been read or data that needs to be written

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10
Q

What is the CIR used for?

A

current instruction register (CIR) - holds current instruction being executed, divides it into operand and opcode

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11
Q

What is the data bus used for?

A

-a bi-directional bus (data/bits can be carried in both directions)
transports data and instructions between components

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12
Q

What is the address bus used for?

A

transmits the memory addresses specifying where data is to be sent to or retrieved from

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13
Q

What is the control bus used for?

A

-a bi-directional bus (data/bits can be carried in both directions)
transmits control signals between internal and external components

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14
Q

What type of signals are given out by control buses? (6)

A

-bus request: shows that a device is requesting the use of the data bus

-bus grant: shows that the CPU has granted access to the data bus

-memory write: data is written into the addressed location using this bus

-memory read: data is read from a specific location to be placed onto the data bus,

-interrupt request: shows that a device is requesting access to the CPU

-clock: used to synchronise operations

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15
Q

In the decode phase of the FDE cycle, what is the instruction divided into? Where?

A

opcode and operand
-in the CIR

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16
Q

What do we mean by opcode?

A

a section of the instruction used to determine what type of instruction it is and what hardware is needed to execute it

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17
Q

What do we mean by operand?

A

a section of the instruction which tells us the address of where the operation is performed

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18
Q

What is the FDE cycle?

A

fetch-decode-execute cycle is the sequence of operations that are completed by the cpu to execute an instruction

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19
Q

What happens during the fetch phase of the FDE cycle? (4)

A

-address from PC is copied to the MAR
-instruction held at that address is copied to MDR via data bus
-simultaneously, the contents of the PC increment by 1
-value held in MDR is copied to the CIR

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20
Q

What happens during the decode phase of the FDE cycle? (1)

A

the contents of the CIR are split into operand and opcode

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21
Q

What happens during the execute phase of the FDE cycle? (1)

A

the opcode is executed on the operand

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22
Q

What is pipelining?

A

the process of completing the different stages of the FDE cycle simultaneously

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23
Q

What are some limitations of pipelining? (2)

A

-programs with lots of branched instructions may not benefit from the effects of pipelining
-some instructions may need to be flushed if the instruction branches off

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24
Q

What are the different types of computer architecture? (3)

A

-von neumann
-harvard architecture
-contemporary processing

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25
Q

What characteristics does Von Neumann architecture have?

A

-shared memory and data bus used for both data and instructions
-includes a single control unit, registers and memory units

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26
Q

What are some advantages of Von Neumann architecture? (2)

A

-cheaper to develop since the control unit is easier to design
-programs can be optimised to design

27
Q

What characteristics does harvard architecture have?

A

-physically separate memory for instructions and data

28
Q

What are some advantages of harvard architecture? (2)

A

-faster to use as pipelining is possible
-both memories can be different sizes

29
Q

What are some characteristics of contemporary processing/architecture? (3)

A

-combination of both harvard and von neumann architecture
-uses von neumann when working with the data and instructions in main memory
-uses harvard when working with cache

30
Q

What are some factors affecting CPU performance? (3)

A

-clock speed
-number of cores
-cache

31
Q

What is clock speed and how does it affect the CPU performance?

A

-the number of clock cycles completed in a second (measured in Ghz)
-faster clock speed, faster performance

32
Q

What do we mean by a core and how does it affect CPU performance? What are some limitations with this?

A

-an independent processor able to execute its own FDE cycle
-more cores, more FDE cycles able to be completed
-some programs aren’t optimised for use of more than one core

33
Q

What is cache and how does it affect CPU performance?

A

-small memory location located on or near the CPU, holds frequently used data
-quicker to access instructions from cache instead of main memory
-as it fills up, unused instructions get replaced

34
Q

What are the different types of cache and what are their properties?

A

Level 1- very fast, small capacity
Level 2- relatively fast, medium sized capacity
Level 3- slower, much larger capacity

35
Q

What are the two types of instruction sets?

A

RISC (reduced instruction set computers)
CISC (complex instruction set computers)

36
Q

What are some characteristics of a RISC processor? (4)

A

-small instruction set
-each instruction= 1 line of machine code
-used in common computers
-pipelining is possible= 1 instruction takes 1 clock cycle

37
Q

What are some characteristics of CISC processors? (4)

A

-large instruction set
-instructions are built into hardware
-used in microcontrollers and embedded systems
-many specialised instructions

38
Q

What are some +/- of CISC? (2 +/- each)

A

+ CISC
-compiler has to do less work
-less RAM required to store the code

-CISC
-increased energy consumption
-may take more than 1 clock cycle to complete

39
Q

What are some +/- RISC? (2 +/- each)

A

+ RISC
-lower energy requirement
-can support pipelining

-RISC
-heavy use of RAM (can cause bottlenecks-processing capability is limited due to the RAM being insufficient)
-compiler has to do more work

40
Q

What is a GPU?

A

graphics processing unit
-a co-processor (an additional processor used for specific tasks) made up of lots of independent processor

41
Q

What are the features of a GPU? (3)

A

-efficient at carrying out simple tasks on larger data sets
-can carry out SIMD (single instructions on multiple data)
-can work in parallel

42
Q

What is a GPU mainly used for? (5)

A

initially used for graphics processing

-weather modelling
-password cracking
-machine learning
-data mining
-doing complex calculations

43
Q

Compare a GPU to a CPU (2)

A

-GPUs are efficient at carrying out simple tasks on larger data sets whereas CPUs are efficient at carrying out complex calculations on small data sets
-GPUs can carry out one instruction on multiple pieces of data while CPUs cannot

44
Q

What are multicore processors?

A

CPUs which have multiple independent cores, each completing its own FDE cycle (can carry out pipelining efficiently)

45
Q

What do parallel systems do?

A

accomplish tasks (also through pipelining) using a single core and threading (the capacity of a program to utilize different processors)

46
Q

What are some examples of input devices? (5)

A

-keyboards
-webcams
-mouse
-scanners
-microphone

47
Q

What are some examples of output devices? (3)

A

-speakers
-printers
-projectors

48
Q

What are the three types of storage? Give examples (3 each)

A

Optical
-CD
-DVD
-Blu-ray

Magnetic
-hard disk drives
-magnetic tapes
-floppy disk

Solid state
-solid state drive
-flash memory card
-USB stick

49
Q

What are some +/- of optical storage? (2+, 3-)

A

+ cheap
+portable

-slow access times
-fragile
-limited/low capacity

50
Q

What are some +/- of Magnetic storage? (3 each)

A

+large capacity
+low cost per GB
+suitable for long term storage & backup

-not durable (has moving parts)
-slow read/write times
-not portable

51
Q

What are some +/- of solid state storage? (3+, 2-)

A

+durable
+fast read/write times
+portable

-high cost per GB
-sometimes has limited capacity
-can wear out after a certain number of write cycles

52
Q

What are the factors to consider for storage? (5)

A

-capacity
-speed
-cost
-durability
-portability

53
Q

What are the two types of primary storage?

A

-RAM (random access memory)
-ROM (read-only memory)

54
Q

What does volatile mean?

A

if something is volatile, when its power is lost, its information is also lost

55
Q

What is RAM? (3)

A

-fast, volatile memory
-can be written to and read from
-used to store temporarily store data and programs that the computer/CPU is currently using

56
Q

What is ROM? (3)

A

-non-volatile memory
-can only be read from
-stores the computer’s start-up routine (bootstrap/BIOS)

57
Q

What is virtual storage?

A

storing information remotely e.g cloud storage

58
Q

What are some +/- of virtual storage? (4+, 5-)

A

+data can be accessed anytime from any device as long as there is internet access
+data can be easily shared without the need for removable media transfer
+easy to collaborate
+can back up data

-can be expensive
-if connectivity is poor, access times can be slow
-if there isn’t an internet connection, you can lose access to files
-if data is stored in a different country, other laws apply
-privacy concerns (relying on a third party)

59
Q

How does INP make use of registers?

A

when INP is used, the ACC stores a value

60
Q

How does OUT make use of registers?

A

when OUT is used, the value is currently in the ACC

61
Q

How does LDA make use of registers?

A

data from RAM goes to MDR (with help of MAR)

62
Q

How does STA make use of registers?

A

value from ACC goes to MDR then sent to RAM (with help of MAR)

63
Q

How do BRA/BRZ/BRP make use of registers?

A

comparison takes place in ALU

64
Q

How does ADD/SUB make use of registers?

A

carried out in ALU, result stored in ACC

OCR A-level Computer Science (8 decks)

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