2: Types of Processor

Question 1

What is a processor instruction set?

Answer 1

Set of all instructions written in machine code that can be recognised and executed by a given processing unit/CPU

Question 2

What happens if an instruction is read that doesn’t occur in the instruction set?

Answer 2

An error flag is produced and the computer halts that program tree.

Question 3

RISC

Answer 3

-Reduced Instruction Set Computer
- Provides a fairly small and basic instruction set where in every operation cycle only one value is fetched or stored from/to memory

Question 4

CISC

Answer 4

-Complex Instruction Set Computer
- The instruction set is much more varied and one instruction can do an entire sequence of operations across multiple clock cycles

Question 5

GPU

Answer 5

-A specialised CPU designed for the manipulation of memory for the image or screen output of a computer.
- Also acts as a parallel processor to increase the performance of the system even in situations that do not involve 3D graphics

Question 6

GPGPU

Answer 6

• General-purpose graphics processing unit
• Acts as a stream processor, a form of parallel processing where a steam (or flow) of data is fed through the processor to perform vector based calculations.
• These are much faster than the conventional CPU and are beginning to be used as computational power in supercomputers

Question 7

Why would a GPU be better in an embedded system rather than a CPU?

Answer 7

• Helps to process images and graphics on the system
• Performance of machine would significantly decrease if CPU was used as it is not designed to specialise in this type of processing.

Question 8

Advantage of GPGPU

Answer 8

the ability to parallel process in the background whilst the CPU continues to process other data.

Question 9

Parallel Processing

Answer 9

The processing of program instructions by dividing them between multiple processors or processor cores

Question 10

Aims of CISC

Answer 10

To complete the task in as few lines of assembly as possible

Question 11

Aims of RISC

Answer 11

To use simple instructions that will be executed within a single machine/clock cycle.

Question 12

How CISCs make use of the compiler

Answer 12

CISC instructions resemble the original command from a high-level language
- The compiler has to do very little work to translate the high level language statement into assembly

Question 13

How RISCs make use of the compiler

Answer 13

There are more lines of code required in the assembly version of high level code
- The compiler has to do more conversion work

Question 14

How are RISCs more efficient?

Answer 14

Require fewer transistors and less complex hardware, leaving more room for general-purpose registers and cache

Question 15

What is a co-processor?

Answer 15

Any additional processor used for a specialised task

Question 16

Purpose of a co-processor

Answer 16

To improve the overall speed of the computer by executing concurrently with the main CPU

Question 17

CPUs excel at … while GPUs excel at …

Answer 17

• Complex operations on small data sets
• Simple operations on large data sets

Question 18

What kinds of data must be assigned before GPUs can render graphics?

Answer 18

• All segments of image given XYZ co-ordinates
• Every segment would be assigned a texture/pattern
• A light source would be assigned and given an angle, brightness and how it falls on the wire frame
• A camera source would be chosen for the image

Question 19

What calculations are required to render graphics?

Answer 19

• 3D arithmetic using XYZ co-ordinates
• RGB calculations
• XYZ positions are typically stored as floating point, so lots of floating point operations

Question 20

How do GPUs render graphics?

Answer 20

After calculations are completed, they are run through every pixel of the finished image from the camera’s perspective and generate the 2D representation of the 3D space

Question 21

Why are GPUs better at rendering graphics than CPUs

Answer 21

• Huge number of calculations done in parallel
• The result of one RGB calculation is not dependent on another
• Mass calculations done in GPUs can take full advantage of parallel processing
• A CPU may perform one floating point operation quicker than a typical GPU, but a GPU will be able to perform a thousand floating point operations much quicker due to the benefits of parallel processing

Question 22

Examples of computing tasks performed by GPUs

Answer 22

• Oil exploration
• Weather modelling
• Machine learning
• Linear algebra
• Statistical analysis
• Stock option predictions
• Gravitational field theory

Question 23

What is a multicore processor?

Answer 23

Single chip containing two or more independent processing units/cores

Question 24

Factors that can further enhance the performance of multicore processors

Answer 24

• On-chip shared cache
• Inter-core communication

Question 25

Why doubling the number of cores does not double the performance

Answer 25

• Overheads involved with inter-core communication
• Some programs can’t make maximum use of all cores

Question 26

Objective of parallel processing

Answer 26

Run a program in less time

Question 27

How parallel processing could be achieved 1

Answer 27

Assigning separate processors or processor cores to the stages of the FDE cycle

Question 28

How parallel processing could be achieved 2

Answer 28

The processors or processing cores carrying out a single job split into tasks, with each task able to execute on any unit.