Clash Of The OC'd Titans: Athlon XP 2300+ vs. Pentium 4/3000

Overclocking In Detail: Athlon XP With 1866 MHz

The fastest AMD processor to date is the Athlon XP 2000+ with 1666 MHz. The manufacturer delivered a CPU that was factory-fitted with a fixed multiplier, which we promptly unlocked according to our previous experience. You can read about this process in the article "Plastic Surgery: Releasing the Athlon XP To Hit 2000+ " and see it in the accompanying video "Second THG Video: Unlocking The Athlon XP/MP ."

In order to attain the maximum increase in clock speed in an Athlon XP 2000+, it is necessary to lower the multiplier from 12.5 to 12.0. In the test, the Athlon ran stably up to a clock speed of 1866 MHz - at clock speeds even higher than this, it was no longer possible to conduct the benchmark tests. A clock speed of 1866 MHz corresponds to an Athlon XP 2300+.

At this point, we should explain why we lowered the multiplier to 12.0: on the one hand, a clock rate of 1866 MHz cannot be achieved with an Athlon XP 1900+ that is factory-equipped with a multiplier of 2.0. On the other hand, it is necessary to set the FSB clock and memory clock as high as possible, so that the memory performance required for such a high CPU clock is available. Take the Quake III benchmark, for example, which gives you a visual comparison between the two multiplier settings (12.0 and 12.5) at an identical CPU clock speed.

In the latest Athlon XP processors with the Palomino core, the maximum multiplier value is 12.5, which is technically limited. Every Socket 462 board has only four registers available for coding the CPU multiplier. Things will look different though, once AMD's Athlon XP 2200+ (Thoroughbred core) makes its debut at the CeBIT 2002 in March. With an FSB of 133 MHz, a board would have to offer a multiplier of 13.5 - AMD solves this problem with a translation table in the CPU. A further possibility is that the multiplier, as delivered with the board, would be fully ignored and that the CPU would dictate the settings.

CPU Voltage: 1.92 Volt For The Athlon

An important condition for successful overclocking is the increase in CPU core voltage. AMD Athlon XP 2200+ processors from the factory work with 1.75 Volt. At such a setting, it is nearly impossible to increase the clock speed by a substantial amount. Extreme clock speeds of up to 1900 MHz are possible only if the CPU core voltage is increased to 1.90 Volt. Also, an increase in core voltage automatically causes an increase in the switching speed of the transistors, as well as a higher thermal power. The large amount of heat generated can be controlled by an efficient watercooling system. Otherwise, the processor will die a thermal death (see our video: Hot Spot - How Modern Processors Cope With Heat Emergencies ). Only a few boards with the VIA KT266A chipset offer a core voltage of more than 1.85 Volt. In the test, we use the Gigabyte GA-7VTXH, which allows a maximum of 1.92 Volt. Epox EP-8KHA+, a well-known and frequently used board, only allows a maximum of 1.85 Volt, which is not optimal for extreme overclocking. The only way to remedy this with the Epox is to modify the voltage regulator.