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mike@mikeshardware.co.uk

Overclocking

CPU

Items that are the most noteworthy are in Bold. Items which have not been filled in ('-') are not considered worthwhile overclocking. Items marked with a ? are yet to be filled in.

* These are the results of my 11 Celeron 366 CPU overclocking tests:

• 413Mhz - 12 (100%)
• 523Mhz - 11 (92%)
• 550Mhz - 5 (42%)

Other test results:

Pentium III 550E Slot 1 - 733Mhz, 133Mhz FSB, 1.65v (default)
Pentium III 600E Slot 1 - 800Mhz, 133Mhz FSB, 1.65v (default)
Pentium III 600E FC-PGA - 800Mhz, 133Mhz FSB, 1.60v (default)
Pentium III 650E FC-PGA - 800Mhz, 123Mhz FSB, 1.60v (default) (813Mhz Max at 1.70v)

Celeron 566 FC-PGA - 850Mhz, 100Mhz FSB, 1.70v (1.5v is default)

AMD Duron 650 - 900Mhz, 100Mhz FSB, 1.75v (1.5v is default)
AMD Duron 650 - 900Mhz, 100Mhz FSB, 1.75v (1.5v is default)

Note that the Athlon (Classic) core overclock column assumes you have the ability to change the clock multiplier with the use of a 'Golden Finger' device such as those available from Trinity Micros (USA) and Ninja Micros (UK).

The Athlon (Thunderbird) and Duron overclocking tables assume that you have unlocked the clock multiplier and are using a motherboard which allows you to change the clock multiplier. See the Hardware Tips page for more information.

For Pentium III overclocking, the lower speed, 100Mhz FSB varieties are the best units to have. Their low clock multipliers (5x to 6x) and relatively slow speeds allow them to be significantly overclocked by setting the FSB speed to 133Mhz.

It should be noted that on a BX-based motherboard, you should choose a 1/4 PCI multiplier to avoid overclocking your PCI slots and IDE controller. If you do not, you are very likely to corrupt the contents of your hard disk and even damage PCI peripherals!! You should also take care when choosing a graphics card if you plan to work on a BX board. You will have no problem with PCI cards, as the PCI bus is not overclocked, but you may have difficulties if you are using an AGP card. Many AGP cards cannot work on the 89Mhz bus speed produced when overclocking the FSB to 133Mhz. Some of the best boards are those based on GeForce256, although even these are not guaranteed to work! If you cannot test the board before purchasing, it is best to either use a PCI graphics card, such as a Voodoo 3, or get a motherboard designed for the 133Mhz FSB speed, such as those based around VIA's Apollo Pro 133A or Intel's i815 chipset. Such boards will not overclock the AGP bus at a 133Mhz FSB speed.

The overclockability of Athlon Classic processors depends largely on whether the processor is produced on a 0.25 micron or 0.18 micron process. 0.18 micron processors can reach 800Mhz or more. If you look on the top of the casing to the right of the 'AMDK7nnnXXXXXX' label you will see either the letter 'C' (0.25 micron) or 'A' (0.18 micron).

The overclockability of Athlon Thunderbird processors will depend on their site of manufacture (Texas or Dresden). Athlon's manufactured in Dresden are more overclockable than their Texan counterparts due to the Dresden CPU's being manufactured with Copper (rather than Aluminium) interconnects. Generally speaking, the higher clocked Athlons are manufactured with a Copper process in Dresden whilst the lower clocked parts use Texan Aluminium interconnects.

Below is a table of Front Side Bus speeds and their associated PCI and AGP clocks.

Items in Red are potentially dangerous or unstable settings.

Graphic Chips

It should be noted that all GeForce based cards, apart from those from Elsa, are built around the nVidia reference design. The only differences between these boards are the memory speeds (5 or 5.5ns) and types (SGRAM, SDRAM, DDR SDRAM), the featureset (e.g. DVI ports, S-Video output, TV Output, Hardware monitoring etc) and the software bundle. The overclocking opportunities are based purely on the memory type and a bit of luck! It is also worth noting that all DDR GeForce cards contain the same Infinion 6ns DDR SGRAM, so the memory overclock on a DDR card is purely based on luck. A 166Mhz memory clock should be achievable due to the memory speed being 6ns (166Mhz).

Items that are the most noteworthy are in Bold.

Memory speed conversion chart

Note that whilst memory is guaranteed for the above operational speed, properties of the board design (trace lengths etc) may prevent the memory from being clocked at its rated speed.