Tech-PC have posted a review of the AMD Athlon XP1800+ CPU combined with the VIA KT133A Chipset and this maybe of interest to some out there.

In the second of our budget upgrading features we answer another question many people pose to us looking for cheap extra performance, "Is it worth running an XP1*00 in my older mainboard?"
It has been nearly two years now since VIA introduced the KT133a chipset. The KT133a added support for the 266 MHz FSB (133 MHz double pumped) front side bus, for the AMD processors. Also the KT133a still kept support for the 200 MHz FSB (100 MHz double pumped) front side bus. This let the user have the options of running either the older first and second Generation Thunderbird processor, or the Duron processor and now the new AthlonXP processors.