AGP/PCI overclocking related?

[AMD FanBoy]

Well i though i read something about a month ago that when you overclock it changes the speeds of your pci and agp slots....is this true?

[NiTrO bOiE]

Yes, it's true unless you apply the AGP/PCI frequeny lock.

[InThrees]

AGP / PCI speeds are determined basically in one of two ways:

Either the motherboard uses a divider, applied to the CPU FSB, to determine the speed, or

The motherboard locks the speeds at a user specified amount.

Example A, KT333 based board running at 133mhz FSB, 1/4 divider is used. 133/4 = 33. At 166, a 1/5th divider is used if one exists, 166/5 = 33. (Agp = PCIx2, so technically the dividers are called 4/2/1 and 5/2/1) At 180mhz, the result would be 35mhz for PCI, with a 1/5 div.

Example B, an NForce2 chipset motherboard can lock the PCI/AGP frequencies at proper freqs, regardless of FSB.