When you overclock you are running the cpu faster than it was designed for which makes it run hot, so its a fine line between getting a safe temperature and a stable speed. This is done for each overclock machine as every chip is different, the amount a cpu can be overclocked depends on many things even down to the sand the thing is made from.
When we get a stable overclock the last thing you want is BIOS "boosting" in a hurr durr, lets add 20% to the clock speed durrr way. a 3.8 overclock becomes a 4-4.2 overclock and the chip dies.