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Overclocking In Detail: Athlon XP With 1866 MHz

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

Processor Memory Clock CAS Latency Type of Memory
Athlon XP 2300+ 155 MHz 2.5 DDR-SDRAM (DDR333, PC2700)
Athlon XP 2200+ 150 MHz 2.5 DDR-SDRAM (DDR333, PC2700)
Athlon XP 2100+ 144 MHz 2.0 DDR-SDRAM (DDR333, PC2700)
Athlon XP 2000+ 133 MHz 2.0 DDR-SDRAM (DDR266, PC2100)
Athlon XP 1900+ 133 MHz 2.0 DDR-SDRAM (DDR266, PC2100)
Athlon XP 1800+ 133 MHz 2.0 DDR-SDRAM (DDR266, PC2100)
Athlon XP 1700+ 133 MHz 2.0 DDR-SDRAM (DDR266, PC2100)
Athlon XP 1600+ 133 MHz 2.0 DDR-SDRAM (DDR266, PC2100)
Athlon XP 1500+ 133 MHz 2.0 DDR-SDRAM (DDR266, PC2100)
Athlon 1400 133 MHz 2.0 DDR-SDRAM (DDR266, PC2100)
Athlon 900 100 MHz 2.0 DDR-SDRAM (DDR266, PC2100)

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 Clock (MHz) Multipl. L1
FSB100 FSB133 X 1 2 3 4 5
500 667 5.0 open open open open open
550 733 5.5 open open open open open
600 800 6.0 open open open open open
650 867 6.5 open open open open open
700 933 7.0 open open open open open
750 1000 7.5 open open open open open
800 1067 8.0 open open open open open
850 1133 8.5 open open open open open
900 1200 9.0 open open open open open
950 1267 9.5 open open open open open
1000 1333 10.0 open open open open open
1050 1400 10.5 open open open open open
1100 1467 11.0 open open open open open
1150 1533 11.5 open open open open open
1200 1600 12.0 open open open open open
1250 1667 12.5 open open open open open
Free closed closed closed closed closed
CPU Clock (MHz) Multipl. L3
FSB100 FSB133 X 1 2 3 4
500 667 5.0 closed closed open open
550 733 5.5 open closed closed open
600 800 6.0 closed open open closed
650 867 6.5 open open closed closed
700 933 7.0 closed closed open open
750 1000 7.5 open closed closed open
800 1067 8.0 closed open open closed
850 1133 8.5 open open closed closed
900 1200 9.0 closed closed open open
950 1267 9.5 open closed closed open
1000 1333 10.0 closed open open closed
1050 1400 10.5 open open closed closed
1100 1467 11.0 closed closed open open
1150 1533 11.5 open closed closed open
1200 1600 12.0 closed open open closed
1250 1667 12.5 open open closed closed
Free X X X X
CPU Clock (MHz) Multipl. L4
FSB100 FSB133 X 1 2 3 4
500 667 5.0 open closed closed open
550 733 5.5 open closed closed open
600 800 6.0 open closed closed open
650 867 6.5 open closed closed open
700 933 7.0 closed open open closed
750 1000 7.5 closed open open closed
800 1067 8.0 closed open open closed
850 1133 8.5 closed open open closed
900 1200 9.0 open open closed closed
950 1267 9.5 open open closed closed
1000 1333 10.0 open open closed closed
1050 1400 10.5 open open closed closed
1100 1467 11.0 closed closed open open
1150 1533 11.5 closed closed open open
1200 1600 12.0 closed closed open open
1250 1667 12.5 closed closed open open
Free X X X X

CPU Voltage: 1.92 Volt For The Athlon

Processor CPU Clock Clock Multiplier CPU Core Voltage
Athlon XP 2300+ 1866 MHz 12 1,920 V
Athlon XP 2200+ 1800 MHz 12 1,920 V
Athlon XP 2100+ 1733 MHz 12 1,920 V
Athlon XP 2000+ 1666 MHz 12.5 1,750 V
Athlon XP 1900+ 1600 MHz 12 1,750 V
Athlon XP 1800+ 1533 MHz 11.5 1,750 V
Athlon XP 1700+ 1466 MHz 11 1,750 V
Athlon XP 1600+ 1400 MHz 10.5 1,750 V
Athlon XP 1500+ 1333 MHz 11 1,750 V
Athlon 1400 1400 MHz 10.5 1,750 V
Athlon 900 900 MHz 9 1,750 V

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.

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