A hacker who goes by the name of Czernobyl discovered that all AMD processors starting with the Athlon XP have a secret developer mode built in. This debug mode can be used by AMD engineers during the development process to ensure that everything is working correctly, it can only be accessed by entering the right values into the CPU's registers.
Using a brute-force approach, Czernobyl has now managed to discover what these keys are, granting access to the debugging features for anyone to enjoy. In theory, this will open up a whole new set of tools and possibilities for hacking, debugging and reverse engineering.
This particular hack is still very early in development though, and comes with the very clear warning that "the item is WORK IN PROGRESS, but USABLE hence released AS IS". Unfortunately, this makes the chance of inputting an incorrect key value all the more likely - a mistake that will instantly crash the entire system.