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Processors

RISC vs CISC/Intel vs AMD by butchrecon
Posted: 3 Jun 01

I have seen many times a post on the difference between RISC and CISC, and Intel and AMD. I will attempt to address those differences as easily as I can. (If I am wrong on something or make a mistake email me and let me know so I can update this FAQ.)

CISC stands for complex instruction set computer and is the name given to processors that use a large number of complicated instructions, to try to do more work with each one.
RISC stands for reduced instruction set computer and is the generic name given to processors that use a small number of simple instructions, to try to do less work with each instruction but execute them much faster.

The Intel x86 instruction set is CISC in design. It contains a large number of instructions, some of which can perform some rather complicated functions, and can require many clock cycles to execute. BUT.......

These latest processors do more than blur the line between the two they really use both! The internal execution core of this type of CPU is actually a "machine within the machine", that functions internally as a RISC processor but externally like a CISC processor. The way this works is explained in more detail in other sections in this area, but in a nutshell, it does this by translating (on the fly, in hardware) the CISC instructions into one or more RISC instructions. It then processes these using multiple RISC execution units inside the processor core.

This design has been created to allow PC processors to reap the benefits of RISC instruction sets while maintaining compatibility with existing Intel x86 code. The internal RISC core is more suited to implementing many of the more advanced performance-enhancing architectural features, as well as being easier to run at much higher clock speeds. Faster clock speeds mean less time to perform each instruction, and therefore it makes sense to chop the large, complicated CISC Intel x86 instructions into more "digestible" pieces to gain performance as clock speeds exceed 200 MHz. From the user's perspective, this additional layer of translation is totally invisible, since it happens entirely within the processor itself.

The K5 and K6 series are internally a highly parallel RISC processor using an x86 decoding front-end. It appears that the AMD Athon processors steer away from this a tad and go to more of the Hybrid design Intel is using (not that this is not hybrid). Though its tuff finding info on these I will keep searching and post the updates.

As far as processors, which one is better? AMD? Intel? Well that all depends on the knowledge of the user and what its purpose is going to be.

Intel:
WIDELY recognized not only in the industry but also by non-informed users. The Pentium name is recognized by nearly everyone who is or will be interested in purchasing a computer. IntelÆs massive advertising campaign has seen to that. Intel has always until recently been the major innovator of chip design. Introducing the Pentium processor and its design, which in turn other companies have attempted to duplicate. The Pentium II architecture was yet another innovation by Intel as was the Socketed 370 design. Intel introduced the MMX instruction set in the Late 1990Æs behind which most processors today still incorporate.
The purpose of the MMX instruction set extension is to provide a hardware performance boost for certain types of multimedia programming. In particular, MMX instructions are designed to allow processing of large amounts of similar data at once, using a single instruction. This is sometimes called single instruction multiple data, or SIMD. This is the origin of the name "matrix math extensions", since these instructions operate on a matrix of data. These types of instructions are especially useful for computations needed in processing graphics, video and audio, which leads to its other name ("multimedia extensionsö) Since MMX is an instruction set extension, this means that processors that support it will run all the software that ran on early processors, but not the other way around; MMX processors are backward compatible. In order to gain the performance benefits of the MMX instructions, software must be specifically written to take advantage of them. This software must detect whether or not the processor supports MMX, because non-MMX processors cannot process the MMX instructions at all. It is possible for software to be written that will handle both MMX and non-MMX processors, just using different code for each in the areas where MMX instructions are used.
Intel processors run at rated speed in Megahertz, which is a combination of System Bus Speed and internal CPU clock multiplier. The Pentium series Processor has always been a staple in the Server and Desktop publishing market. It is used in the gaming industry and is quite stable. Its high cost compared to comparable processors has always set it apart until recently.

AMD:
AMD's entry in the fifth generation processor sweepstakes is called the K5. This processor was eagerly awaited and it was hoped that it would provide a viable alternative to the Pentium early in the Pentium's life cycle. Unfortunately, AMD delivered the processor over a year late and at much lower clock speeds than had been originally anticipated. As a result instead of being the "Pentium killer" AMD had hoped for, the K5 was positioned as a low-cost Pentium alternative. The K6 Series are very advanced processors internally. They uses x86 translation/emulation, decoding x86 instructions into what it calls RISC86 operations. It compares internally very similarly to the Pentium Pro and the Pentium II processors, which work in a similar way. One trend that AMD has continued quite well with the K6 is its reputation for compatibility. The K6 is not a direct clone of the Pentium family at all, because it is its own design. However, K6 chips work with what are at least to my knowledge very few if any compatibility issues. Since the K6 does run on socket 7 motherboards, it is an excellent choice for upgrading provided that the voltage issues are dealt with. A BIOS upgrade is often also required to enable the K6 to be recognized by the BIOS. With the K6 II/K6 III Series of processors AMD introduced a new technology called 3D Now!. 3DNow! technology, the first innovation to the x86 architecture that significantly enhances floating-point-intensive 3D graphics and multimedia applications, uses SIMD (Single Instruction Multiple Data) and other performance enhancements to enable a superior visual computing experience. Introduced as a key feature of the AMD-K6-2 processor in May 1998, 3DNow! technology has more than a nine-month time-to-market head start over competing CPU-based 3D enhancement technologies. The worldwide installed base of 3DNow! technology-enhanced PCs has grown to more than 12 million systems. AMD processors with 3DNow! technology span the complete range of desktop and mobile computing, from sub-$1,000 PCs to high-performance laptops based on the Mobile AMD-K6-2 processor to high-end multimedia desktop systems powered by the new AMD-K6-III processor. The AMD K7 Athlon Introduced a ôPentium IIö Style Processor that in some areas out performs the PII /PIII.
Now in the Socketed 370 style called Socket A, The Athlon continues to give High performance at low cost. Now that AMD is starting to outperform Intel in areas such as gaming, and with their low cost compared to Intel, the PC world has begun to embrace the AMD Athlon as an alternative for home computer needs.

As for which is better, neither is really any better than the other. The Intel Still is favored for High-end desktop and Server solutions. The AMD still is focused on home PCÆs and ôGamersö. Which is best will be an age old debate that will never likely end. Now that both companies later this year will introduce a 64bit processor, the war should continue into the Server market.

Before you run out and purchase a PC consider what you want to do with it along with your budget. If you want to keep cost low and would like excellent performance, then the Athlon series should be a good fit. As well with gaming the Athlon series should be an excellent choice. If your looking at Desktop publishing and A strong Server oriented PC, then the Intel series processor is what you should get.
Personally I feel that for the money the AMD Athlon processors are the better buy. But this is my opinion.

Please keep in mind that the opinions in this article are just that, opinions. Feel free to contact me if you have comments or questions.

I would Like to mention that some of the content in this article came from AMD.com, pcguide.com, and Intel.com.

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