1.1.2 Types Of Processors

Question 1

instruction set

Answer 1

• is a group of commands for a CPU in machine language
• the instruction set will vary from one processor to the next
• there are 2 types of processors :
  - CISC
  - RISC

Question 2

CISC (complex instruction set computer)

Answer 2

• Consists of a larger instruction set which includes more complex instructions [1]
• As the instructions are more complex, they can take multiple clock cycles to execute. [1]
• instructions are built into the hardware
• instructions take up less space in memory
  - eg. MULT A,B (requires much less lines of code compared to RISC)

Question 3

RISC ( Reduced instruction set computer )

Answer 3

• consists of a smaller instruction set with more simple instructions [1]
• each instruction is one line of machine code
• so takes one clock cycle per instruction [1]
• so suited to pipelining
• usually used in smartphones and tablets

Question 4

Features of RISC

Answer 4

• has fewer transistors [1]
• so require less power [1]
• so increase their power efficiency making them ideal for usage in low-power devices like mobile phones
• cheaper to manufacture
• has fewer general purpose registers
• because RISC has simpler instruction set, instructions can be executed faster and so programs run faster
• takes up more space In memory / requires more RAM to store the code (as there is more lines of codes)
• suited to pipelining so more instructions can be executed in the same amount of time so programs run faster

Question 5

CISC features

Answer 5

• has more transistors
• so requires more power
• has more general purpose registers
• used in laptops and desktops
• Has more addressing modes
• compilers are less complicated
• takes up less space in memory/ less RAM required since code is shorter
• more expensive to manufacture
• not suited to pipelining so programs run more slowly

Question 6

CROSS-compatibility

Answer 6

• a program written for a RISC processor won’t work on a CISC processor vice versa
• a program written for a RISC processor won’t necessarily work on another RISC processor as they may have different instruction sets

Question 7

GPU ( graphics processing unit )

Answer 7

• is a co-processor made of lots of Independent processors
• the GPU is responsible for processing graphics within the computer to reduce load on the CPU
• a GPU can either be part of the graphics card or embedded in the CPU

Question 8

GPU & CPU comparison

Answer 8

• CPUs are general purpose processors whereas GPUs are specifically designed for graphics [1]
• GPUs are likely to have built in circuitry or instructions for common graphics operations [1]
• GPUs can perform an instruction on multiple pieces of data at one time [1]
• this is useful when processing graphics
• e.g transforming points on a polygon or shading pixels
• this means it can perform transformations to onscreen graphics quicker than a CPU

Question 9

GPU uses besides graphics

Answer 9

• 3D modelling
• Data modelling
• financial modelling
• Data mining
• machine learning
• calculations on multiple data at the same time

Question 10

SIMD Processing ( single instruction multiple data)

Answer 10

• a computing method that enables processing of multiple data with a single instruction
• GPUs support SIMD processing as they are designed to perform the same operation on multiple pixels or vertices simultaneously
• this is a common requirement in image processing, simulations and machine learning

Question 11

GPU benefits

Answer 11

• it isn’t possible to use only a GPU as the CPU assigns tasks to the GPU
• parallel processing : GPUs can handle many tasks simultaneously as they are multicore processors
• faster execution: as GPUs can use parallel processing, they can speed up tasks, particulary involving large amounts of data or complex computations.
• GPU’s can perform more calculations per unit of power consumed in comparion to CPUs making them more energy efficient when it comes to parallel tasks

Question 12

Multicore SYSTEMS

Answer 12

• A multi-core system has multiple cores (processing units) in a single processor which can each independantly process instructions concurrently
• when a computer has multiple cores, it can utilise parallel processing

Question 13

Parallel processing

Answer 13

• Definition: Cores work together on the same task or on separate tasks concurrently.
• Application: Enhances efficiency by dividing tasks among cores.

Question 14

Parallel processing can be achieved by

Answer 14

• using multi-core processors
• utilising more than one processor eg. CPU and GPU

Question 15

Benefits of multicore processors

Answer 15

• Multitasking:

Definition: Each core handles a different task simultaneously. ( this is useful when a user has multiple applications open at the same time )

• Background Tasks:

Issue: Single processor systems can slow down with background tasks.

Solution: Multicore processors allocate background tasks to separate cores.

• Improved Responsiveness:

Advantage: Even if a program becomes unresponsive, other tasks continue smoothly on other cores.

Question 16

Why would using a RISC processor rather than a CISC result in increased battery life ?

Answer 16

• RISC has a smaller instruction set [1]
• requires fewer transistors [1]
• so requires less power [1]