A bloke managed to get an Intel Celeron D Processor overclocked from 3.06 GHz to 8.19 GHz.

TiN_EOF's overclocking efforts seem to have set a new record for an overclocked processor's speed. Intel Celeron D 347 which contains the NeBurst architecture based in the Cedar Mill core (65nm). According to the extreme systems forum, Tin_EOF's specs included a D347 lapped, then IHS-removed and polished. Also under the bonnet was an Xtremelabs.org MAGNUM Legend Edition copper pot, DFI Lanparty UT P35-T2R and some very fast Nidec fans. It also used a OCZ 1GB DRAM, a Radeon 7000 VE, a PCI and a ENERMAX Revolution85+ 1250W

“To get few MHz more, decided to make some insane step forward - remove IHS from CPU. As we know, all latest Intel CPU's have soldered IHS to die with indium metal. it have +170°C melting point. IHS is quite thick, near 1.5-2mm and is bit a barrier for high-end LN2 cooling, where each degree is a need. Thanks to my cpu, it had no coldbugs even with all pot full with boiling LN2,” he wrote.

Obviously this chucked out a lot of heat. Actually far too much heat and the whole lot caught fire. But before it did it recorded its blistering speed. Ah well the brightest bulbs burn the fastest.