The architecture of a microprocessor is designed to run programmes that get the desired output based on a specific input. The two common microprocessor architectures predominately used today are the contrasting RISC vs CISC.  Each of these two architectures has its own advantages and disadvantages in speed, ease of use for programmers, and practical application. Presented here are descriptions of these two architectures, and five key differences in RISC vs CISC.  

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The performance of a processor can be expressed in the time it takes to run a programme. This is determined by how many instructions are in a programme, how many cycles are in each instruction, and how much time is required for each cycle.
However, optimizing computer performance by balancing time, cycles, and instructions is only part of the picture. Different microprocessor architectures place different demands on RAM and compiler technology. They also have different costs to the consumer, and the acceptance in the commercial world is not always quick to change. Comparing RISC vs CISC is anything but straightforward.      

What Is RISC?

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RISC stands for Reduced Instruction Set Computer. It is a type of microprocessor architecture that only uses simple instructions that are most frequently used in programs. It implements less common, more complex instructions using subroutines, or simpler instructions. RISC microprocessors use pipelining to allow the various stages of the instructions to be processed simultaneously and thus more efficiently.  

What Is CISC?


CISC stands for Complex Instruction Set Computer. It is a type of microprocessor architecture that contains a large set of computer instructions and commands, from simple to complex. Some of these instructions may only be used rarely in programs. CISC is actually the predecessor of RISC; the terms were only coined when RISC was developed to differentiate between the two. Because RISC came second, CISC tends to be used as a catch-all term for any microprocessor design that is not RISC.

5 Differences: RISC vs CISC

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There are many differences between RISC and CISC microprocessor architectures.  Here the five most important ones are described.  

1. Built-In Instructions and Pipelining

2. Instructions Per Program, Cycles Per Instruction, and Pipelining

3. Register Memory Architecture

4. Code and RAM Requirements

5. Emphasis On Hardware Vs Software


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In the past, computers used CISC based microprocessors. Only more recently was RISC based processing developed, and the two terms were coined. The dramatic reduction of the cost of RAM and improved compiler technology means that RISC architecture, and its focus on software vs. hardware, has found its place in the market. RISC microprocessors are used across many platforms, from cell phones to tablets to supercomputers. In general, speed is higher, and power consumption is lower in RISC vs CISC.

CISC based microprocessors still remain important, particularly in personal computers. The x86 instructions are standard for Windows, which is optimized for CISC microprocessors and requires much more code for a RISC microprocessor than a CISC one. Personal computers currently use both RISC and CISC microprocessors, depending on the brand.

However, the line delineating RISC and CISC microprocessors is beginning to blur. RISC microprocessors remain defined by their single cycle instructions, and their load/store architecture, and their larger number of general purpose registers. However, CISC chips are starting to make use of pipelining. Increased transistor density allows more CISC-like instructions to be built into RISC microprocessors. In fact, many of today’s RISC microprocessors use as many instructions as CISC chips of the past.  

As advances continue, pitting RISC vs CISC against each other is no longer so simple.