The MHz Myth Part 2 – Where Intel Falters

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Hopefully now, more of you are aware as to why it is so important to us as consumers and AMD as a company to gauge performance by the combination of the IPC and frequency, and not just the frequency alone. There are two different areas that a company, either AMD or Intel can improve the total performance of a processor.

The first category of improvement is in the frequency. Technology has pushed the frequency improvements with process shrinks. These “Process Shrinks” are in fact just smaller geometries and faster transistors in the core of the CPU. Design has also driven the frequency increases by enabling deeper pipelines and having fewer gates per clock cycle. This second frequency enhancement, on a side note, can also hinder architectural performance so the manufacturer must find the correct mathematical limit to the pipelines and gates.

The other category used to enhance total processor performance is by improving the amount of work per clock cycle that is done. Techniques of this that many AMD fans will probably recognize are superscalar architectures, dynamic instruction schedulers, larger on-chip caches and advanced branch prediction. As you might have guessed, many of these are part of the Athlon XP product, and we will discuss them later in the article.

As mentioned before, it is important to note on a technical standpoint that deeper pipelines, on their own, transform in to less work per cycle, thus reducing the IPC part of our performance equation. This reduction in work can be offset by things such as caches and branch prediction, or by forcing the processor into higher frequencies. The graph below shows the Pentium 4 processor as the first Intel processor to step backwards in IPC, or work performed per clock cycle.

It is because of this reduction in work per cycle that Intel is having to push their Pentium 4 line of processors up to higher clock frequencies to be competitive even against the current Athlon Thunderbird processors or even to beat out its own Pentium III line of CPUs.

AMD has chosen to NOT follow Intel’s approach and is working to maintain a balanced approach to optimizing their Athlon line of processor’s performance in both areas: IPC and Frequency. Referencing the graph below, you can see that when comparing the Athlon 1.4 GHz to a processor of 300 MHz faster frequency, the AMD chip is still ahead by a considerable amount in nearly all the benchmarks.

Due to results like this AMD believes the Pentium 4 processor will continue to be forced to drive frequency to remain competitive with AMD Athlon processor in terms of real-world application performance.

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