A processor, or say more precisely CPU (Central Processing Unit ) can be defined as an integrated circuit that is responsible for processing stored instructions. The primary operations of a CPU are:
– Fetch : Receiving instructions from memory
– Decode – Convert it into binary instructions
– Execute – Operation is performed
– Store – Saving output to memory
It can have two types of CPU architecture, CISC and RISC. Both provides communication between hardware and software.
These CPU architectures are capable of carrying out primary CPU tasks, though, they follow different approaches. The main difference between them is, CISC supports more instruction sets than RISC.
Basis | RISC | CISC |
---|---|---|
Stands for | Reduced Instruction Set Computer | Complex Instruction Set Computer |
Size of instructions | Smaller and simpler instructions | Larger and Complex instructions |
Execution Time | 1 cycle per instruction | Multiple number of cycles per instruction |
Emphasis | On Software | On hardware |
Instruction Formats | Fixed (4 bytes) | Variable Length (2-6 bytes) |
Control Unit | Hardwired Control Unit | Microprogrammed Control Unit |
Data and Instruction Cache | Separate | Combined |
Example of processors | ARM processor and Qualcomm processor are some examples | AMD, VAX and Intel x86 CPUs are some examples |
CPU size | Smaller | Larger as they have larger instruction libraries |
Addressing Modes | Fewer | Many |
Array | Not Supported | Supported |
Pipeline | Easy | Hard |
Power consumption | Less | More |
Referred as | Machine Oriented | Programmer Oriented |
Register sets | Has multiple register sets | Has Single register set |
Memory unit | Doesn't have memory unit | Have memory unit |
It stands for Reduced Instruction Set Computer.
It is basically conceptualized on the fact of making hardware simpler and less complex. And this is done by implementation of the Instruction set which reduces the load on processes like loading, storing and evaluating data.
In other words, it has an assembly language that enables each and every task to be split into simpler instructions which are then executed for each clock cycle. Its instructions are efficient but due to simplicity it processes more lines of code.
It focuses on reducing execution time by optimising and simplifying instruction set. It requires only single clock cycle to process results in uniform execution time. However, it reduces efficiency in case of large program size which leads to need of more RAM for storing instruction.
RISC architecture is often used in portable devices such as mobile phones.
It stands for Complex Instruction Set Computer.
It is basically based on complex hardware and all the importance is given to that always. This is done by implementing complex hardware which serves as a single instruction for all the processes like loading, storing and evaluating data.
In other words, It processes larger and more complex assembly instructions each time. One CISC instruction can do the task of multiple RISC instructions.
It focuses on reducing the number of instructions per program without considering the number of cycles per instruction. It relatively requires less RAM to store instructions. It is mainly used in desktops or laptops computer.
Multiplying two variables X*Y:
This post was last modified on April 5, 2021