COMPUTER CPU ARCHITECTURE - CISC AND RISC

CPU Architecture

Processor (really a short form for microprocessor and also often called the CPU or central processing unit) is a central element of the computer. This component is vital in a way that is responsible for everything that makes your computer. It defines, at least in part, that may be used operating systems, computer software package that can run, how much energy to use a computer, and how stable the system will be among others. CPU is also an important factor determining the overall system price: new and more powerful processor, the more expensive will be driving.

When the Hungarian born John von Noyman, storing first proposed a series of instructions - to say, a program - in the same memory for data that is really innovative idea. It was his "first draft of the report EDVAC", written in 1945. Report a computer system, organized into four main parts: central arithmetic unit, the central control unit, memory and input / output devices. More than half a century later, almost all processors have Noyman background "architecture.

For several years the two families dominated the computer microprocessor industry - the Intel Pentium and Apple / IBM / Motorola PowerPC Alliance - each CPU is a great example of the progress of time CPU architectures, CISC and RISC.

CISC - Complex instruction set Computer

CISC architecture is a traditional computer, which uses processor microcode to execute very comprehensive set of instructions. This can vary in length and use all addressing modes requiring complex chain decoding them.

For several years, the trend among computer manufacturers to build increasingly complex processors, which are increasingly set of instructions. In 1974, John Cocke of IBM Research decided to try an approach that significantly reduces the number of chip-making instructions. By mid-1980 that led to a number of computer manufacturers reverse the trend of building processors able to perform only a very limited set of instructions.

RISC - Reduced instruction set Computer

RISC processors rate held constant training, the prohibition of indirect addressing mode and retain only those instructions, which may overlap and the performance of a machine cycle or less. One advantage of RISC processors is that they can carry out their instructions very fast because the instructions are so simple. Another, perhaps more important advantage is RISC chips, which require fewer transistors, which makes them cheaper to design and produce.

There is still considerable controversy among experts regarding the ultimate value of RISC architectures. His supporters argue that RISC machines are both cheaper and faster, and therefore cars in the future. Skeptics note that by making simple hardware, RISC architectures put a greater burden on the software - RISC compilers have to generate a software routine to perform complex instructions that are performed in hardware CISC computers. They say that this is not a valid conventional microprocessors trouble because they are increasingly making fast and cheap anyway.

To some extent, the argument is moot because CISC and RISC are conversions are becoming increasingly so. Many of today's RISC chips support as many instructions as yesterday of CISC chips and back today CISC chips use many techniques formerly associated with RISC chips. Even champion CISC, Intel, RISC techniques used in its 486 chip and made more and more in its Pentium family of processors.