A set of instructions is what is at every computer's core. Instruction sets are the set of all instructions written in machine code that can be recognised and executed by a given processing unit or CPU. The two main categories are CISC and RISC.
A computer architecture philosophy originated in the late 1980s that aims to simplify hardware by using an instruction set composed of a few basic steps for loading, evaluating, and storing operations. Examples of processors which use RISC architecture Architecture is the term used to describe the different parts of the hardware that are required to allow a computer system to operate things such as the processor, buses and main/cache memory. are MIPS, PowerPC, Atmel's AVR, the Microchip PIC processors, Arm processors, RISC-V. Its memory access is restricted to a few load and store instructions.
The advantages of RISC can be summarised to its simple instructions. Because they allow an easier decoding process, and are quickly executed it results in a faster processing time. Moreover, RISC processors consume less power than CISC processors, which makes them ideal for portable devices.
However, RISC also has its downfalls. Because it works with simple instructions it requires a larger magnitude of instructions to execute a task a CISC processor could execute with fewer more complex instructions. As it has these additional instructions RISC processors require more memory for storage. On top of all of that manufacturing RISC processors can be more expensive than CISC processors
CISCs try to complete a task using as few lines of assembly as possible. The processor hardware and circuitry have to be more complicated so can understand and execute a series of operations. An instruction may take more than one clock cycle to be executed; as they are larger than one-word size.
This type of archetype is mainly found in desktop computers and laptops.
The advantages of CISC processors surround the fact it requires a reduced code size to perform complex tasks. Its complex instructions can perform multiple operations, this can result in a more memory-efficient code. On top of that, CISC processors have a larger user base and thus more available software than RISC processors; as CISC has been used for a longer time.
Although the more complex instructions have great benefits, they also make the processors take longer to execute such instructions, as more time is necessary to decode them, which consequently will cause such processors to consume more power than RISC processors. The complex instruction sets also pose a greater level of difficulty to design and manufacture CISC processors rather than RISC ones.
