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A OCR Computer Science A level > Chapter 3 - Types of processor > Flashcards

Chapter 3 - Types of processor Flashcards

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1
Q

What is the stored program memory concept?

A

» Machine code instructions are fetched and executed serially by a processor that performs arithmetic and logical operations

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2
Q

How is the machine code fetched in Von Neumann’s architecture?

1 Mark

A

» Are fetched from memory one at a time, decoded and executed in the processor

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3
Q

Name 5 descriptions of Von Neumann’s architecture.

5 Marks

A

» Shared memory space for instructions and data
» Can access instructions and data required using a dedicated bus
» Single Processor CU manages program control and single ALU
» Same bus used for transferring both instructions and data
» Uses FDE cycle to excute one isntruction at a time in a linear sequence

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4
Q

What is the one problem of Von Neumann’s architecture and the 2 advantages?

A

» The data bus is slower than the rate at which the CPU can carry out instructions - Von Neumann Bottleneck - CPU has to wait for the data transfer as it is much faster
» Simpler operating system
» Easy to program

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5
Q

What is Harvard architecture extensively used in?

A

» With embedded Digital Signal Processing (DSP)

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6
Q

What is DSP?

A

» The DSP applications include audio and speech signal processing, sonar and radar signal processing and digital image processing

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7
Q

What are embedded systems?

1 Mark

A

» Special purpose computers built into devices often operating in real-time, such as those used in navigation systems

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8
Q

Name 4 descriptions of Harvard architecture.

4 Marks

A

» Memory is split into 2 parts
» One part for data and another part for program instructions
» Each part is accessed with a different bus
» Allows for pipelining

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9
Q

Why is data and instructions being fetched with a different bus an advantage?

1 Mark

A

» Allows the CPU to pipeline as the CPU can fetch both data and instructions at the same time

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10
Q

Can Harvard architecture be faster than von Neumann’s architecture?

A

» Yes because data and instructions can be fetched in parallel instead of competing for the same bus and avoids von Neumann bottlenecks

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11
Q

What is the one comparison between the Harvard and Von Neumann architecture in terms of where they are conventionally used?

1 Mark

A

» Von Neumann - used in conventional processors in PC’s
» Harvard used in DSP

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12
Q

What is the one comparison between Harvard and Von Neumann’s architecture in terms of memory?

1 Mark

A

» Von Neumann - data and programs share the same memory
» Harvard - the instructions and data are held in separate memories

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13
Q

What is the one comparison between the Harvard and Von Neumann architecture in terms of buses?

1 Mark

A

» One bus is used to transfer data and instructions - Von Neumann
» Parallel data and instruction buses may be used - Harvard

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14
Q

What is the one comparison between Harvard and Von Neumann’s architecture in terms of size?

1 Mark

A

» Programs can be optimised in size - Neumann
» Programs tend to be large - Harvard

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15
Q

What does CISC stand for?

1 Mark

A

» Complex Instruction Set Computer

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16
Q

What is the instruction set?

1 Mark

A

» Set of all instructions written in machine code, that can be recognised and executed by a given CPU

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17
Q

What is the aim of a CISC processor?

1 Mark

A

» Aims to complete the task in few lines of code as possible

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18
Q

What is complex instruction?

A

» Combines a load/store instruction with the instruction that carries out the actual calculation

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19
Q

With a CISC processor, what is so special about the hardware?

A

» Processor hardware and circuitry has to be more complicated so it can understand and execute a series of operations within one instruction
» Therefore more expensive

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20
Q

How many clock cycles do complex instructions take to execute and why?

A

» Takes more than one clock cycle, because its performing multiple operation

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21
Q

What are the three advantages of a CISC processor?

3 Marks

A

» Quicker to code programs
» Compiler has very little work to do to translate a high-level language statement into machine code
» Since code is short - requires less RAM is required to store the instructions

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22
Q

What are the three disadvantages of a CISC processor?

3 Marks

A

» They are larger as they require more transistors, making them more expensive
» Take multiple cycles per line of code, therefore programs run more slowly due to comploicated circuit
» Pipelining is not possible

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23
Q

What does RISC stand for?

1 Mark

A

» Reduced Instruction Set Computer

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24
Q

What does RISC aim to do?

1 Mark

A

» Aim to use simple instructions that will be executed within a single clock cycle

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25
Q

How are complex commands such as MULT represented in a RISC processor?

A

» Separated into a number of simpler commands

26
Q

Why does the compiler have to do more work in a RISC processor?

1 Mark

A

» Since there are more lines of code

27
Q

Why do the RISC instructions require fewer transistors?

1 Mark

A

» Because they have less complex hardware

28
Q

What are the 4 advantages of a RISC processor?

4 Marks

A

» Simpler processor designe
» Easier to pipeline - As fixed length of codes
» Decode unit has a lower power consumption
» Faster than CISC as programs run faster due to simpler instructions

29
Q

What are the 2 disadvantages of a RISC processor?

2 Marks

A

» Compiler has to do more work to translate high-level code into machine code
» More RAM is required to store the machine code

30
Q

Where are RISC and CISC architectures used?

2 Marks

A

» RISC is used mainly in portable devices
» CISC although less common, are used in Desktops and PC’s

31
Q

What is a co-processor?

1 Mark

A

» Is an extra processor used to supplement the functions of the primary processor for a specialised task, and carries out only a limited range of functions

32
Q

What is a Multi-core processor?

2 Marks

A

» Single-chip containing more than one independent processing units
» Each core can fetch decode and execute an instruction independently
» Focuses efforts of multiple CPUs into 1 task

33
Q

What is parallel processing?

1 Mark

A

» Multiple processors are executing more than one task at the same time by dividing the program instruction between the multiple cores

34
Q

What is a GPU?

A

» A specialized electronic circuit that is very efficient at manipulating computer graphics and image - processing
» Contains specialised processing cores, created to render images
» Can work quickly over a large block of similar data - Due to having large number of cores - which are higly paralleiziable

35
Q

What is a GPU a form of?

A

» A Co-processor which can be used with a CPU to acclerate performance

36
Q

What is one difference between multi-core systems and parallel processing?

1 Mark

A

» They accomplish a similar task however instead of requiring multiple cores they can complete task with a single core by using threading

37
Q

Compare RISC and CISC

5 Marks

A

» CISC - Each instruction takes more than one clock cycle to execute - RISC - Each instruction executes in one clock cycle
» CISC - High power consumption - RISC - Low power consumption
» RISC - Simple processor design - CISC - Complicated processor design
» RISC - Complex task can only be performed by combining multiple instructions - CISC - Complex instruction can be performed using less instructions
» RISC - Pipelining is possible - CISC - Pipelining is not possible

38
Q

What is concurrent processing?

2 Marks

A

» One processor is executing more than one task seemingly at the same
» With each processing in turn being given a slice of processor time

39
Q

What are some limitations of parallel processing?

3 Marks

A

» Algorithm must be suitable for parallel processing
» Increased complexity of the control unit, which means increased time spent managing processes instead of executing them
» Potential for deadlock, where one process requires the output of another

40
Q

What are 2 ways parallel processing can be achieved in modern computer systems?

2 Marks

A

» Multiple processors within a single computer, each dedicated to a specific task, such as a GPU
» Multiple cores inside a single CPU, running multiple process simultaneously

41
Q

Why is a GPU more suited for processing graphics than a CPU?

4 Marks

A

» CPUs are general purpose processors, whereas GPUS are designed specifically for graphics, so are likely to have built-in circuitry for graphic operations

» GPUS are able to perform an instruction on multiple data locations at the same time

» We want to do this when processing graphics
» Which means it can process and perform transformations to onscreen graphics faster than the CPU

42
Q

What is SIMD?

2 Marks

A

» Single instruction, multiple data, is a type of parallel processing
» Hardware components that perform the same operation on multiple data operands concurrently

43
Q

What is an array processor architecture?

A

» Single instruction multiple data
» Allows same instruction to operate simultaneously on multiple data locations

44
Q

Other than graphics, state 2 additional uses of a GPU, and why is it more effective than a CPU at the specific task?

A

» Cryptocurrency mining, Audit processing,machine learning

» Process involved calculations on large data sets
» Single instruction multiple data
» Specialist hardware/ array processing than a CPU

45
Q

Why does simply not doubling the number of cores not double the performance?

A

» Some programs cant make maximum use of all cores
» Overheads involved with inter-core communication

46
Q

What is MMID?

2 Marks

A

» Multiple instruction multiple data
» Different instructions carried out at the same time on different pieces of data

47
Q

What does a GPU Process?

A

» Involved processing many calculation on large data sets SMID

48
Q

What are 2 benefits of a multicore system and one disadvantage?

3 Marks

A

» More jobs can be carried out in a short time because they are executed simultaneously
» Task can be shared between processors to reduce the load on individual processor and avoid bottlenecks

» Hard to program code to decompose problems efficiently for multicore processing

49
Q

What is a CPU bottle neck?

A

» A bottleneck occurs when a PC is running a demanding application and its performance begins to stall.

50
Q

Why do supercomputers have multiple GPUs and cores?

A

» Cost-effective method
» GPU tend to have a large number of cores so can run highly parallel problems

51
Q

Give one advantage and one disadvantage, other than cost, of using Von Neumann compared with array processor architectures?

2 Marks

A

» Simpler operating system
» Slower than array processing on large data sets

52
Q

What are the 2 different approches to parallel processing?

2 Marks

A

» SIMD
» MIMD

53
Q

Why is a supercomputer useful?

A

» CPUs can work in parallel
» On the same problem

54
Q

Which part of the FDE cycle will the accumulator recieve a value from the ALU?

1 Mark

A

» Execute

55
Q

What might a cotemporary processor contain?

A

» Both a harvard architecture and a Von Neumann architecture

56
Q

What is mean by the term Von Neumann architecuture?

2 Marks

A

» Uses same memory for data and instructions
» Uses same bus for data and isntructions

57
Q

Where would an interrupt be handled?

1 Mark

A

» After the decode phase

58
Q

Describe one difference between CISC and RISC

2 Mark

A

» CISC architecture has more complex circuitry, whilst RISC has simple circuitry minimising manufacture cost

59
Q

What does BRA do?

A

» Accumulator checked to see if value held is positive or zero
» If so BRANCH carried out/jumps to specificed location

60
Q

What is a thread?

A

» A sequence of instructions that have been sent to the CPU to be processed

61
Q

What is the main benefit of multithreading?

A

» Allows 2 threads to be run on each core

62
Q

What is one use of a GPU?

A

» Modelling

A OCR Computer Science A level (75 decks)

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