CISC and RISC Flashcards
What is RISC?
Reduced instruction set computing
A design of processor which has a smaller instruction set than CISC so single CISC requires require multiple instructions in RISC. The hardware is less complex and cheaper. Typically used in smartphones or tablets.
What is CISC?
Complex instruction set computing
A design of processor which has a wider instruction set than RISC and therefore has more silicon circuitry and is more expensive than RISC. Typically used in desktop PCs or laptops.
What are the advantages of RISC?
More cost effective as there are fewer transistors so producing the chip is cheaper. Also the processors use less power and generate less heat.
Supports pipelining as simple instructions such as loading two variables can be done at the same time
Instructions take only one cycle to complete as each instruction is not split into further instructions
Simpler addressing modes allow data or instructions to be fetched quicker
What are the disadvantages of RISC?
Compiler has a more difficult task to convert high-level code into a limited instruction set
Programs require more memory to store a larger number of instructions
Better suited to simpler, low demand task such as running a program on a mobile
What are the advantages of CISC?
Compiler has an easy task to convert high-level code into a larger range of complex instructions
Programs require less memory as there are fewer more complex instructions
What are the disadvantages of CISC?
Less cost effective as there are more transistors required for the complex circuitry so producing the chip is more expensive. The processors use more power and generate more heat
Doesn’t support pipelining because instructions are more complex and difficult to split into stages
Instructions take more than one cycle to complete as reading and writing data from or to memory is included in the complex instruction
More complex addressing modes take longer to fetch data or instructions
Better suited to higher intensity tasks such as high end gaming
