Differencing Between Myths and Facts? Continued

Realizing the negative image normal consumers would receive from seeing lower clocked processors, AMD switched the nomenclature system of its microprocessors to more of a comparison rating. Thus, 1.67GHz Athlon XP "2000+" processors were to perform similarly to 2.0GHz Pentium 4s, overall. As it turned out, Athlon XP processors of even lower ratings (e.g.: "2500+" vs. 2.8GHz P4) outperformed the competition in many benchmarks.

In some benchmarks, applications favored Intel’s Pentium 4 architecture and thus were noticeably superior to comparable AMD products. These applications were mainly related to multimedia and video and sound production/editing. Intel still holds the reins with these benchmarks. It is generally agreed that both companies offer excellent products for their intended application (e.g.: value, performance, etc.), but many still have confusion over why higher clocked processors don’t always perform as well as their lower clocked competitors.

For example, processors may have similar clock rates but one may perform better over the other. The reason is due to the architecture of the microprocessor, which thus determines the clock cycle (rated in megahertz and gigahertz) and the instructions per clock (IPC) that the CPU is able to perform. CPUs with longer pipelines tend to have higher frequencies than their shorter-pipelined counterparts. This is not always a good thing, as the longer the pipeline, the longer it takes for a single instruction to be processed.

As a result, the shorter pipelines in the Athlon XP architecture, for example, results in a lower clock but an overall higher amount of instructions per clock. Now you may be wondering why the number of clock cycles is more heavily looked upon than the number of instructions per clock. For one, IPC only tells you how many instructions per clock the processor can perform and it doesn’t really tell you anything about its performance. The "GHz" and "MHz" ratings do give an overall idea of how well the processor will perform, but there needs to be a general variable that can give someone an idea of a generalized performance rating.

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