bus speed defaults to 133 when I try to go past 200?

[ThePiston]

I have a Shuttle AN35N (Nforce2) and 200mhz ram. My mobo has settings for bus of 133/166/200 and above 200 it goes, 234/235/236, etc. So, if I try to jump up to 234, it won't let me and goes to 133. ANyone know why? I tried scaling the multiplier back accordingly, but still only getting 133. I can go 166 or 200, but not above 200.