Tutorial for overclocking that POS:
Make sure you have dasmmed good cooling (done):
Change the multiplier to as high as it can go (most older Cyrix M2's have a multiplier of no more than 3.5x, which is a remap of the 1.5x multiplier).
I would set it to a 2x multiplier, then raise the FSB until it is unstable. Keep it at that FSB, and raise the multiplier.
If it doesn't work, lower the bus speed and up the multiplier. If you still can't, up the voltage from 2.9, up to, say , 2.9 (you are saying that cooling isn't an issue). 3.2 is the maximum tolerance of the chip, at least, according to the tech docs.
Since you don't care about the longevity of this chip, up the voltage as much as you need (I think the highest you'll be able to get is 3.3v)
To get 3.3v, just change the voltage from dual voltage, to single voltage (used for old pentiums). The I/O voltage of older boards is 3.3v, and when you set the chip up to single voltage, it sets the chip to 3.3v as well.
Some of the chips did, infact, have multipliers up to 4x, but usually not. Remember, Cyrix useed the annoying PR rating.
FWIW, here's a listing of the PR ratings:
PR133: 100/50, 110/55
PR150: 120/60, 125/50
PR166: 133/66, 137.5/55, 150/50, 150/60
PR200: 150/75, 165/55, 166/66, 180/60
PR233: 166/83, 187.5/75, 200/66
PR266: 207.5/83, 225/75 (6x86MX), 233/66 (6x86MX)
PR300: 225/75 (M-II), 233/66 (M-II)
PR333: 250/83
PR366: 250/100
PR400: 285/95
PR433: 300/100