so people, this is my cpu and mobo config:

xp2000+
MSI kt3V (via kt333)

actually my mobo can support up to amd 3000+, i've updated my bios to the latest version available already, before the bios upgrade the support was up to 2800+.

BTW, 2800+ or 3000+ are 333 fsb cpu right? so with a 333 fsb my mobo should set all the bus for the periferal at the right timing, right?

Here is the question, why when i rise the fsb up to 166 x 2, my sistem is running out of spec? (ex. agp@84Mhz)

My mobo chipset is:

Northbridge: KT333
Southbridge: VT8235

Maybe your
Apg and pci are not locked, so that when you go up, it
ups all of them.

This suggests that your motherboard does not support 333FSB. Maybe your manufacturer has included support for it unofficially and expect you to use a PCI/AGP lock feature or simply have these overclocked.

Your AGP is running out of spec because at 166Mhz clock it cannot proberly multiply this number. At 133 you would need a 1/2 multiplier (or divider, if you like). At 166 is seems you are still using this 166*1/2=83Mhz when you really need a 2/5. Perhaps you can manually set this or there is a lock frequency (maintaining 33/66 PCI/AGP at all system clock frequencies).

I believe the 2800 is available at 266FSB and this is probably true for 3000 as well. Perhaps it is these CPUs that have been given support in the BIOS update.

The KT333 can run at 333 FSB, it all depends on motherboard manufacturer as to the dividers; if you have BIOS support then I would guess that you can do it