Breaking the x86 Instruction Set: how to find undocumented x86 instructions
What's the bet the really secret instructions are hidden behind special conditional decode logic? I.e. the cpu wont even ask for the next byte if some register value is not set, possibly a secret register that first needs to be set via some other hidden instruction. Make that a sequence of 3 hidden instructions combined with arbitrary register and immediate values, and you won't get close to identifying them in a billion years.<p>I mean if you worked for Intel and your manager said "make me a really secret instruction" would your best response be "lets just not document it and hopes noone notices"?<p>What I would give to read the full microcode of the latest Intel processor. I am guessing it is stored in a vault with the real nuclear codes, Alien cadavers and the Holy Grail.