i just clocked up my warp engine to 40Mhz just swapping the crystal without changing the cpu. yeah yeah i know, naughty me. :roll: but i had a massive heatsink and fan on there with thermal paste.
ran fine rendering for days and days... :-D
as ever, your mileage may vary, and i take no responsability for any damage caused etc etc. :lol:
--edit--
iirc, warpengines used 25Mhz 040's and clocked them up to 28Mhz, as i seem to remember them doing a deal where you could buy just the board and swap in the CPU off your A3640 card....