Not exactly. There are two pieces to the Athlon overclocking puzzle; the processor core and the L2 cache. Current Athlons have cache chips which are mounted on the same PCB as the processor core but are not part of the core itself. Because the cache chips aren’t built on the same manufacturing process as the processor core, they won’t run nearly as fast as the processor core itself. Thus, the cache chips are set to run at a fraction of the speed of the processor core.
For 500 MHz to 700 MHz Athlons, the cache runs at 1/2 the speed of the processor, or between 250 MHz and 350 MHz. Cache that runs at over 350 MHz is difficult to produce and relatively expensive, so for speeds of 750 MHz to 850 MHz, the cache runs at 2/5 the speed of the processor, or between 300 MHz and 340 MHz. For 900 to 1000 MHz Athlons, the cache runs at 1/3 the speed of the processor, or between 300 MHz and 333 MHz.
This fact is important for two reasons. First, the relaxing the cache timing degrades performance, which creates “flat spots” in the Athlon line. For example, a 700 MHz Athlon and a 750 MHz Athlon are very close to one another from a performance standpoint, because the core clock speed goes up, but the cache speed goes down. The same is true of an 850 MHz Athlon and a 900 MHz Athlon.
Second, this arrangement typically means that the cache will become a limiting factor before the processor core itself will. For example, let’s say you purchase an Athlon 550 manufactured on the .18 micron process. This is the same process used to manufacture the 1000 MHz Athlon, so it’s entirely possible your processor core will overclock to 800 or 900 MHz, or even higher. However, the cache on your 550 will typically run out of steam somewhere between 700 and 750 MHz, effectively limiting the processor to 700 MHz.
