i also have a new k6-3 450 that won't come off.
first do not pry,you could pop the metal cooling plate off the cpu.
it is not held on by grease or even the usual thermal pad.
it is held on by some very hard type of glue/thermal transfer compund that feels like it is made of ceramic.
i have tried to cut it with a razorblade and it didn't seem to have any effect.
remeber, if you are trying to cut that, that the razor blade should be inserted betwen the metal cooling plate and the heat sink and not the heat plate and the cpu.
if you pop off the metal cap which has direct contact with the core, you could destroy it.
i spent way too much to buy this cpu just because i always had a fetish to try to get one to 500mghz. so i don't want to take a chance on breaking it.
if anyone knows the answer to this question, i would like to know it also. many passes with a razor blade failed to make any detectable progress with this very hard heat sink glue/heat transfer stuff. i din't want to keep trying to cut it since it wasn't doing anything. worst case would be cutting a groove around the glue and then not being able to cut it lose completely,which would reduce the size of the heat trasfer patch causing it to overheat. although breaking the cpu or poppin the heat plate or breaking the cpu might top that. if i knew it could be done and that someone had done it,then iwould continue going round and round with a razor blade for the next 2 weeks because i believe if i could water cool it i could get it to do 500 stable. the other thing might be to make a cooling device for the mb l3 cache as that seems like a road block to higher speeds as well.
btw mine is running at 4.5 x 105 for 472.5
i was able also to get the fsb to 110 and 115 but had to turn off l3 cache and reduce mghz to do it, altough at around 440 and 115fsb it was almost as fast as 472.5.
crippling the L2&L3 cache is not a real overclocking option
as the higher mghz does not make of for the performance hit of doing that. good luck. greg lee