1.1.2 - types of processor

Question 1

Complex instruction set computers (CISC)

Answer 1

A large instruction set is used to accomplish a task in as few lines of assembly language as possible.

Question 2

advantages of CISC processors

Answer 2

• Compiler has to do very little work
• Very little RAM required to store instructions

Question 3

disadvantages of CISC processors

Answer 3

• Only about 20% of the specialised instructions were used in the average program.
• Cannot benefit from pipelining.

Question 4

reduced instruction set computers (RISC)

Answer 4

Only simple instructions, each taking one clock cycle to be executed.

Question 5

advantages of RISC processors

Answer 5

• Since each instruction takes one clock cycle, pipelining is possible.
• Takes single clock cycle.

Question 6

disadvantages of RISC processors

Answer 6

• Compiler has to do more work to translate high level code into machine code
• More RAM required to store machine code instructions

Question 7

co-processor

Answer 7

An extra processor used to supplement the functions of the primary processor. It generally only carries out a limited range of functions like floating point arithmetic and graphics processing.
e.g,GPU

Question 8

GPU

Answer 8

A GPU has a massively parallel architecture consisting of thousands of smaller, more efficient cores designed for handling multiple tasks simultaneously. Its highly parallel structure makes it suitable for tasks where
processing of large blocks of visual data is done simultaneously

Question 9

Name some more generalised uses for GPUs in computers.

Answer 9

• machine learning
• oil exploration
• image processing
• financial transactions

Question 10

instruction set

Answer 10

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

Question 11

Name the 2 types of instruction sets.

Answer 11

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

Question 12

multicore processor

Answer 12

A single processor containing more than one processing unit which can process instructions at the same time.

Question 13

Name 3 ways multicore processors increase performance.

Answer 13

• Each core can fetch, decode ad execute its own instructions.
• On-chip shared cache
• Inter-core communication

Question 14

Name 2 reason why double cores doesn’t mean double performance.

Answer 14

• Overheads involved with inter-core communication (bottlenecks, waiting on other processes).
• Some programs can’t make maximum use of all cores.

Question 15

parallel processing

Answer 15

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

Question 16

2 limitations of parallel processing

Answer 16

• The task being carried out.
• If the software is designed to make use of parallel processing.

Question 17

How would parallel processing increase the performance of a computer system? (3)

Answer 17

• multiple instructions processed simultaneously
• shortens overall time taken
• different cores can tackle different components simultaneously

Question 18

Compare CISC with RISC. (4)

Answer 18

CISC: many instructions are available, complicated processor design
RISC: limited number of instructions available, simple processor design

Question 19

Why are GPUs better suited for graphics handling than CPUs? (3)

Answer 19

CPU is general purpose whereas GPU are specifically designed for graphics
Likely to have built in circuitry for common graphics operations
SIMD so can perform transformations to onscreen graphics faster than CPU

Question 20

Describe why a supercomputer will be useful for breaking encryption. (2)

Answer 20

The CPUs can try multiple keys simultaneously to break the code.