who has tried over clocking the at89c51 in KEIL C? how fast can it go? 10% 20% 100%? post your results.
i will try liquid cooling [with water?????] and tell you my results.
You should also try the 22 nm CMOS technology. I hear it may allow you to run in the GHz range.
Liquid cooling is only relevant if the chip is overvolted. At stock voltage, it is likely to hang (or produce incorrect results) long before it gets hot enough to care about that extra cooling.
If not, then it is way better to use a TEC (Peltier) and run the chip at sub-zero temp - a lower temp makes a chip faster.
The thing to remember with a 8051 chip is that it hasn't any PLL. So can't just reconfigure to try higher and higher speeds. You either need to replace the crystal, or connect a programmable oscillator instead of the crystal.