Well most of the new chipsets have the agp/pci bus locked at 66/33mhz so thats not really a concern anymore. But in general the mobo would run that bus on the 1:5 ratio so if your chipset does not lock that bus then more you jump the system clock then more you jump your bus. This will cause you AGP card and anything in the PCI slots to be overclocked and cause all sorts of system instability and cause hardware damage to the Graphic Cards and PCI cards. Make sure you keep the AGP/PCI bus at 66/33mhz and if your mobo has the option to adjust the ratio then utalize it to keep the bus stable..
Barton 2500+ @ 2200mhz (10x220 vcore @ 1.8)
Asus A7N8X Dlx 440 FSB
1gb Geil GD pc3500 Dual Channel (2-3-3-6)
Segata 80gb SATA 8.5ms seek
ATI Radeon 9800 Pro(420/720)