RISC vs CISC processors

Question 1

What is RISC?

Answer 1

Reduced instruction set computer, aims to use simple instructions that will be executed within a single machine/clock cycle

RISC architectures typically have a larger number of registers.

Question 2

What is CISC?

Answer 2

Complex instruction set computer, completes a task in as few lines of assembly as possible

CISC designs are generally more complex than RISC.

Question 3

CISC features

Answer 3

Used in laptops/ desktops computers. X86 processors made mainly by intel and AMD​

Hs more complex hardware​

Larger number of complex instructions of variable length​

Multiple machine/clock cycles per instruction​

Physically larger, more complex circuity, requires more silicon to make, typically more expensive​

Greater energy consumption​

Cant make use of pipelining​

As emphasis is on the hardware, the complier (software) has to do less work​

Small code sizes, higher cycle per second​

Makes more efficient use of RAM than RISC ​

Multiple addressing modes available

Question 4

RISC features

Answer 4

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Used in smartphones, tablets, embedded systems. Made popular by ARM processors​

Has simpler hardware​

Smaller number of simple, standardized instructions that are all a fixed length​

Single machine cycle per instruction​

Smaller in size, less complex circuitry required, less silicon, typically cheaper to produce​

Lower energy requirements​

Can support pipelining​
​
Large code sizes, lower cycles per second​

Heavy use of RAM