RISC stands for Reduced Instruction Set Computer. The design strategy of a RISC processor includes limiting the number of instructions. This does not mean that ALL RISC processors have less instructions than ALL CISC processors, but in general, they do.
8051 is a CISC but having less number of instruction as comared to ARM which is RISC.CISC
CISC: Complex Instruction Set ComputerRISC: Reduced Instruction Set Computer
CISC and RISC are the two categories that are used to classify CPU architecture. CISC is an acronym for complex instruction set computer.
RISC is faster than CISC
In CISC, the instruction set is very large that can be used for complex operations while in RISC the instruction set is reduced, and most of these instructions are very primitive. CISC computer's execution time is very high whereas RISC computer's execution time is very less. In, CISC code expansion is not a problem while in RISC code expansion may create a problem. In CISC, decoding of instructions is complex whereas, in RISC, the decoding of instructions is simple. CISC requires external memory for calculations, but RISC requires external memory for calculations. CISC has only a single register set while RISC has multiple register sets are present.
character of risc -load store architecture -fixed length instruction -hardwired control instruction -pipelined implementation character of cisc -many instruction that access memory directly -large number of addressing mode -variable length instruction code -support of misaligned accesses answer by sachita pandey
RISC - Reduced Instruction Set Computer CISC - Comples Instruction Set Computer
CISC, or Complex Instruction Set Computing, provides a rich instruction set that has instructions for many different types of operations, e.g. logic, math, floating point math, and so forth. RISC, or Reduces Instruction Set Computing, has a much sparser set of instructions that allow you to do very much less with each instruction. Because the individual instructions are simpler, a RISC chip can execute many more instructions than a CISC chip in a certain amount of time. Additionally, because it needs many fewer transistors, a RISC chip can be built to use much less power than a CISC chip, even with power saving techniques like temporarily turning off unused parts of the chip. In modern computing, examples of CISC chips are the Intel Core and Atom series. Example RISC chips are the ARM and PowerPC chips.
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Short answer: CISC instructions consist of several RISC instructions. That makes CISC slower (per instruction) compared to RISC.Compared to other architectures, CISC processors have relatively powerful instructions, which used run so called microprograms. For each instruction, the corresponding microprogram has to be fetched and executed, which is considerably slower than just using 'real' hardware instructions (compare RISC). According to wikipedia, microprogrammed processors are no longer common. Instead, a special unit resolves CISC instructions to RISC instructions.