Introduction

The war rages on

The last 12 months we've witnessed an extraordinary tug of war between CPU manufacturers AMD and Intel. Not surprisingly, this battle really heated up last summer when AMD originally announced their Athlon processor.

Initially launched in clock speeds of up to 650MHz, the Athlon gave AMD a performance advantage over Intel's latest processor for the first time in the company's history. Of course, Intel quickly followed with their own processor launch - the Pentium III "Coppermine." Based on the same basic architecture as previous Pentium III processors, the major additions to the Coppermine variant of the Pentium III core are 256K of L2 cache and the use of the smaller, more advanced 0.18-micron manufacturing process.

Why is cache so important?

While the amount of L2 cache was reduced from 512K to 256K with Coppermine, the L2 cache was now running at the same speed as the processor core. The net result is a performance improvement that scales higher as the clock speed of the processor increases.

L2 cache is a type of high-speed memory used by processors to store data that are necessary to complete a given operation. Both processors feature two types of cache memory: L1 and L2. (also known as Level 1 and Level 2)

L1 cache is the first place the processor looks for the data it needs, if it can't find the information there, it next looks in the L2 cache. While L1 cache is always integrated on the processor core, (running at the same speed as the processor) this doesn't always ring true for L2 cache. In the case of the original Athlon CPU, the L2 cache was (at best) running at half the speed of the processor core. As a result, as the Pentium "Coppermine" Pentium III got faster, its L2 cache also got faster. Meanwhile, the L2 cache on the older Athlon CPU never exceeded 350MHz.

Because of this, at higher clock speeds, the Pentium III began to gain on (and eventually overtake) the Athlon. We first demonstrated this in our Athlon 800 review; in the article our Pentium III 750 slightly outperformed the Athlon 800, this occurred despite the 50MHz advantage the Athlon enjoyed.

Frankly, we weren't surprised by the results; we've witnessed this for almost two years now with the Intel Celeron line of processors. While Pentium II and older Pentium III processors ran with half-speed L2 cache, the Celeron has always had full-speed L2 memory. Despite only containing 128K of L2 cache, these Celeron processors offered very similar performance in comparison to the more expensive Pentium processor equivalent.

So what is AMD's answer to these faster Pentium III processors? Simple. Integrate the L2 cache on the processor core itself.