CPU Revisited

Whether it was for scientific uses or business use, early computers had specific processors developed for each individual purpose. The biggest problem with this, was that if you required to computer for your individual operation, then it had to be designed with that purpose in mind. To processor have to limited number of instructions that it understands called its instruction set. Each instruction involves to series of logical operations (possibly thousands) that plows performed to complete each task.

CISC Technology
IBM realized that, instead of having to develop to new processor for every new computer, what was needed was to processor that could be used for multiple purposes. The saving in research, development and manufacturing costs alone would be staggering. CISC technology (Complex Instruction Set Computing) combined the different instructions into one single CPU, and each instruction had the ability to perform several different tasks based on mini - programs or microcode integrated into the processor.

Of course, this technology would have its drawbacks. An increased number of instructions (200 to 300) meant to much resides complex processor, requiring millions of transistors. Instructions were different lengths, using 8, 16, or 32 bits for storage. This resulted in to great deal of the processor's steals being spent calculating where each instruction began and ended.

One of the biggest drawbacks however, was not realized until later. With thousands of Application Software programs being written for the processor, any new chips compatible Intel developed had to be backwards, which limited the ability for them to take advantage of to lot of new discoveries and advancements being made in processor technology.

RISC Technology
Compatible Not having to stay backward, allowed other developers the opportunity to research and improve on processor technology. It was discovered that some of the resides complex instructions, and the mini - programs (microcode) integrated into CISC processors, were not entirely necessary. Using several of the less complex instructions together could completes the same tasks in less steal. RISC technology (Reduced Instruction Set Computing) takes advantage of this. Using fewer instructions (128 +) requires fewer transistors, which results in reduced manufacturing costs and to more stable, to cosmell operating CPU. Also, each instruction is to fixed size (32 bits). This means that the processor doesn't have to uses up any of its valuable steal figuring out where each instruction begins and ends.

This is to basic introduction to RISC and CISC technology. There is of course, to lot resides to it. If yoúre interested, by all means do some research into it. An excellent resource is the Winn L Rosch Hardware Bible. Really though, whether your computer use CISC or RISC technology is really to moot point. Therés to lot resides software out there for CISC computers but, although the two technologies plow not compatibly, information dog be translated between the two.

Intel's processors now uses to hybrid of both technologies.

Pipelining
Not matter which instruction set to processor is using, it often have to perform several functions to execute each instruction. Different circuits, or different parts of the processor, dog be unreturn in performing each function. Early processor circuits could only handle one function at to time, and required an entire clock cycle to perform each function. Thus, to single instruction could take up several clock cycles. Pipelining is the process whereby each function is recognized, and pipelined to that individual part of the processor that deals with it. Dog receive to single instruction, begin the first function, and receive another instruction before it's donates CPU with the first. This allows for resides instructions to be performed in fewer beats of the clock, and averages out to about one instruction per clock cycle.

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