NEW 1.1.2 Types of Processor

What does 'CISC' stand for?

• Complete Instruction Set Controller

• Complex Instruction Set Controller

• Complex Instruction Set Computer

• Complete Instruction Set Computer

Answer explanation

A Complex Instruction Set Computer (CISC) is a processor design that has a large number of instructions in the instruction set requiring fewer cycles to achieve the same output as a reduced instruction set computer. However, the design is more complex and less power efficient. CISC computers have a large number of addressing modes and a variable format for instructions.

Which processor design does the following statement relate to, 'simple instruction format for the opcode and operand in the current instruction register'?

• Both

• CISC

• RISC

• Neither

Answer explanation

A Reduced Instruction Set Computer (RISC) is a processor design that has a reduced number of instructions in the instruction set requiring many cycles to achieve the same output as a complex instruction set computer. However, the design is simpler and more power efficient making it ideal for portable devices. RISC computers have a limited number of addressing modes and a fixed format for instructions due to their simplistic design.

Which of the following is the best definition for a parallel processor system?

• Development of a CISC architecture with a single set of CPU components

• Development of CISC architecture with several sets of CPU components in one microprocessor

• More than one computer working together to processor a single job

• The simultaneous use of several processors to perform a single task

Answer explanation

A parallel processor system is one which simultaneously uses several processors to perform a single task. A task may be split into a number of sub-tasks each of which may be processed by any available processor.

Which processor design does the following statement relate to, 'compiler has to do more work to convert high level language statements into machine code'?

• Both

• RISC

• CISC

• Neither

Answer explanation

A Reduced Instruction Set Computer (RISC) is a processor design that has a reduced number of instructions in the instruction set requiring many cycles to achieve the same output as a complex instruction set computer. However, the design is simpler and more power efficient making it ideal for portable devices. RISC computers have a limited number of addressing modes and a fixed format for instructions due to their simplistic design.

Which processor design does the following statement relate to, 'more RAM is needed to store the instructions'?

• RISC

• CISC

• Neither

• Both

Answer explanation

A Reduced Instruction Set Computer (RISC) is a processor design that has a reduced number of instructions in the instruction set requiring many cycles to achieve the same output as a complex instruction set computer. However, the design is simpler and more power efficient making it ideal for portable devices. RISC computers have a limited number of addressing modes and a fixed format for instructions due to their simplistic design.

Which of the following is the best definition for 'SIMD'?

• Different operations carried out on the same piece of data at the same time

• A single operation carried out on many pieces of data at the same time

• A single operation carried out on a single piece of data at a time

• Different instructions carried out at the same time on different pieces of data

Answer explanation

SIMD stands for 'Single Instruction Multiple Data', and refers to an operation carried out on many pieces of data at the same time. GPU's are specialised co-processors which are well suited to carrying out SIMD instructions.

Which processor design does the following statement relate to, 'less RAM is required to store program instructions'?

• RISC

• CISC

• Both

• Neither

Answer explanation

A Complex Instruction Set Computer (CISC) is a processor design that has a large number of instructions in the instruction set requiring fewer cycles to achieve the same output as a reduced instruction set computer. However, the design is more complex and less power efficient. CISC computers have a large number of addressing modes and a variable format for instructions.

Which processor design does the following statement relate to, 'the opcode and operand can take a variable number of bits in the current instruction register depending on the command being decoded'?

• RISC

• CISC

• Both

• Neither

Answer explanation

A Complex Instruction Set Computer (CISC) is a processor design that has a large number of instructions in the instruction set requiring fewer cycles to achieve the same output as a reduced instruction set computer. However, the design is more complex and less power efficient. CISC computers have a large number of addressing modes and a variable format for instructions.

Which of the following is NOT a reason why doubling the number of processor cores does not lead to a direct doubling of processor speed and efficiency in all situations?

• There are overheads in terms of communication between multiple cores

• Writing programs to take advantage of multiple cores can be complex

• Multi-core processors are rarely used

• Many problems are not fully parallelisable

Answer explanation

If a problem, is for example only 20% parallelisable than multiple cores will add little benefit, no matter how many you add. On top of this there are certain overheads in terms of communication between multiple cores that mean even a problem which is highly parallelisable will not see a straight doubling of efficiency simply by doubling the number of cores.

Which processor design does the following statement relate to, 'better power consumption makes this architecture better suited to portable devices'?

• RISC

• CISC

• Both

• Neither

Answer explanation

A Reduced Instruction Set Computer (RISC) is a processor design that has a reduced number of instructions in the instruction set requiring many cycles to achieve the same output as a complex instruction set computer. However, the design is simpler and more power efficient making it ideal for portable devices. RISC computers have a limited number of addressing modes and a fixed format for instructions due to their simplistic design.