1.1.2 Types of processor

Question 1

Give facts about a CISC Processor

Answer 1

More complicated processor design
- Uses complex instructions
- Each instruction may take multiple machine cycles
- Does not allow pipelining
- Instructions have variable format and number of bytes
- Longer instruction set
- Many instructions are available
- An instruction can perform complex tasks so no need to combine multiple instructions
- A task may be completed in a single machine cycle
- Many addressing modes are available
- Uses single register set
- Does not have GPRs so needs to constantly send data to and from memory
- Requires less RAM
- Programs run more slowly due to complicated circuit
- Integrated circuitry is more expensive

Question 2

Give facts about a RISC Processor

Answer 2

Simpler processor design
- Uses simpler instructions
- Each instruction takes one machine cycle
- Allows pipelining
- Instructions have fixed format and number of bytes
- Smaller Instruction set
- Limited number of instructions are available
- An instruction performs a simple task so complex tasks can only be performed by combining multiple instructions
- A task may take a number of machine cycles
- Fewer addressing modes are available
- Uses one or more register sets
- Has GPRs to reduce the need to constantly send data to and from memory
- Requires more RAM
- Programs run faster due to simple instructions

Question 3

What are GPUs?

Answer 3

GPUs are designed specifically for graphics so have built in circuity and instruction sets for calculations required in common graphics operations.

Question 4

What are GPUs used for?

Answer 4

GPUs tend to have large number of cores so can run on highly parallelisable problems.

GPUs are able to perform the same instruction on multiple pieces of data at one time (SIMD) so are suited to
processing graphics (e.g. transforming points in a polygon or shading pixels) which means it can perform
transformations to onscreen graphics quickly.

GPUs are becoming a cost efficient way of tackling problems other than graphics processing including:
- subset of science/engineering problems
- modelling physical systems
- data mining
- audio processing
- breaking passwords

Question 5

What are multi-core processors?

Answer 5

Have more than one processor incorporated into a single chip.

Question 6

What is parallel processing?

Answer 6

A computer carries out multiple computations simultaneously to solve a given problem.

Question 7

What are two different approaches to parallel processing?

Answer 7

-SIMD (Single Instruction Multiple Data): The same instruction operates simultaneously on multiple data locations
- MIMD (Multiple Instructions Multiple Data): Different instructions operate concurrently on different data locations

Question 8

What are advantages and disadvantages of parallel processing?

Answer 8

Advantages

-Uses multiple processors working together to perform a single job which is split into tasks so each task may be processed by any processor so the job is completed more quickly.
-Allows faster processing and speeds up arithmetic processes as multiple instructions are processed at the same time and complex tasks are performed efficiently.

Disadvantages

-Parallel processing isn’t suited to all to problems. Most problems are only partially parallelisable.
-Processors are controlled by a complex OS to adapt the sequential algorithms and ensure synchronisation. Programs