200 MHz isnt the physical speed, its double pumped speed, that is the CPU can access memory on both the clock edges. traditionally the CPUs accessed memory in interger multiples of complete cycles, now AMD chips can access memory twice in a single cycle. That is why a 100 MHz FSB can provide a 200 MHz speed.
with VIA chipsets you can however overclock the bus upto 133 MHz (on most boards) and even sometimes beyond that. just make sure you use the rihgt parts. becoz the other parts, especislly the PCI and ISA ards will run at fractional speeds of memory, i.e. 1/3, 1/12 etc. they may not be able to sustain 1/3 of 133.
try increasing the speed in steps of 2 MHz (Abit board supports it I guess)
you can also overclock the CPU by about 30% of its rated frequency. be sure its multiplier x FSB, so higher the FSB do lower the multiplier a bit. and of course, all this is trial and error, check the system for stability for a day or two and go ahead to higher settings if okay.
remember, with each MHz you are stepping closer to the cliff. Hey, I liked the Cliffhanger.
girish