The 100 is probably 1.5 multiplier at 66mhz. Neither were locked so you could play with it at that point, however, you'd need a mobo that could do some modifications. More than likely the board you have can't. See if you can get the specs of the mobo. If you can change either the multiplier(poss.) or fsb(unlikely) then you can try.
I hav a P120 running at 133 Mhz. I didn't have a good mobo (don't even know the brand..). I Just switched the jumpers to a p133 mhz (it supported up to 200 Mhz, no MMX). I couldn't cahenge bus speed and multiplyer, so I just did it that way. And it works
Gave me 5% or 10% more frames in Quake1. The CPU was still pretty cool, and then I hadn't heard of additional cooling.
I couldn't get it to POST or boot at 150 Mhz dough...
I got my old Pentium 75 (was in a Packard Bell) to run completely stable (and cool) at 120 Mhz (2*60) easily with a decent heatsink and fan (wouldn't post at 133, which is the mobo max). I ran extremely cool, and never once locked up or crashed... I've been running it like this for over 6 months now! These original Pentiums seem to be very overclockable.