Difference between RISC and CISC architecture of processors

As far as the processor hardware is concerned, there are two basic types of concepts to implement the processor hardware architecture.

What is RISC architecture?

RISC is acronym for Reduced Instruction Set Computing. In this architecture a microprocessor  is designed to perform a smaller number of types of  instructions so that it can operate at a higher speed (perform more millions of instructions per second, or MIPS). 

Since each instruction type that a computer must perform requires additional transistors and circuitry, a larger list or set of computer instructions tends to make the microprocessor more complicated and slower in operation. That is why less instruction means fast in operations. Pipelining is one of the unique feature of RISC. It is performed by overlapping the execution of several instructions in a pipeline fashion. 

Example: Apple iPod and Nintendo DS etc.

What is CISC architecture?

CISC is acronym for Complex Instruction Set Computing. CISC architecture are designed to decrease the memory cost. The large programs need more storage, thus increasing the memory cost and large memory becomes more expensive. 

To solve these problems, in CISC architecture the number of instructions per program is reduced by embedding the number of operations in each instruction. Thereby the instructions are more complex.

Example: IBM 370/168, VAX 11/780, Intel 80486 etc.

Difference between  RISC and CISC architecture:

#	RISC	CISC
1	Simple instructions taking one cycle.	Complex instructions taking multiple cycle.
2	Very few instructions refer memory.	Most of instructions may refer memory.
3	Instructions are executed by hardware.	Instructions are executed by micro-program.
4	Fixed format instructions.	Variable format instructions.
5	Few instructions.	Many instructions.
6	Complex addressing modes are synthesized in software.	Supports complex addressing modes.
7	Multiple register sets.	Single register set.
8	Highly pipelined.	Not pipelined or less pipelined.
9	Conditional jump can be based on a bit anywhere ¡n memory.	Conditional jump is usually based on status register bit.
10	Complexity is in the compiler	Complexity is in the micro-program
11	Few addressing mode and most instructions have register to register addressing mode	Many addressing modes

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Difference between Microprocessor and Microcontroller

What is Microprocessor ?

A microprocessor is an integrated circuit or  logic chip that is designed to fetch the instructions from other part of the system and executing it performing several logical and arithmetic operations.

On its own, without a surrounding circuit and applied voltages it is quite useless. It will just lie on your workbench staring back at you.

What is Micro-controller ?

A micro-controller is a self-contained system with peripherals, memory and a processor that can be used as an embedded system.

Actually this is a complete microprocessor-based control system built onto a single chip. It is small and convenient but doesn't do anything that could not be done via a microprocessor with  additional components.

Microprocessor Vs Micro-controller:
Among several, some important difference between microprocessor and micro-controller is given below:

#	Microprocessor	Micro-controller
1	Microprocessor contains ALU, control unit (clock and timing circuit), different register and interrupt circuit.	Microcontroller contains microprocessor, memory (ROM and RAM) I/O interfacing circuit and peripheral devices such asconverter, timer etc.
2	It has many instructions to move data between memory and CPU.	It has one or two Instructions to move data between memory and CPU.
3	It has one or two bit handling instructions.	It has many bit handling instructions.
4	MIcroprocessor based system requires more hardware	Microcontroller based system requires less hardware reducing PCB size and increasing the reliability.
5	Access times for memory and I/O devices are more.	Less access times for built-in memory and I/O devices.
6	It has single memory map for data and code	It has separate memory map for data and code.
7	Less number of pins are multi-functioned.	More number of pins are multifunctioned.
8	Microprocessor based system is more flexible in design point of view.	Less flexible in design point of view.

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