A CPU executes the machine instructions of your program (you might think of this as "assembly" programs, like "put a zero in register 12" or "jump to address 0x

A CPU executes the machine instructions of your program (you might think of this as "assembly" programs, like "put a zero in register 12" or "jump to address 0xFF3392"). There have been architectures where instructions map directly onto transistors, but since System/360 (*) there's an extra level: the CPU has it's own, lower-level programming language that's used to execute the machine instructions. Finding out how a CPU actually works is interesting per se, and very valuable for competitors, but this work might also expose vulnerabilities and/or backdoors, built into the chip itself. It seems to be around 100kB of code, so there's a whole lot of opportunity... (*) first commercial architecture I know of...