Dolda CPU-instruktioner.

An enterprising Hungarian engineer, Can Bölük at Verilave, has done something similar, probing the obscure nervous system of Intel’s fabulously complex x86 microprocessors. He’s probed for unused and undocumented opcodes in the chips’ instruction sets. And he’s uncovered quite a bit. His code is available on Github.

If you’ve ever programmed an x86 chip in assembly language, your first thought might be, “I didn’t know there were any unused opcodes.” After all, the architecture has a spectacularly complex and richly well-appointed instruction set that’s been growing steadily since the 1970s. Surely every instruction has been done by now? The opcode map must be full to overflowing?

Nope. There are still plenty of holes in the x86 opcode map, and not all of them are actually empty. Some are just… undocumented. Some instructions appear to be deeply buried maintenance functions while others look like Easter eggs, forgotten bugs, or partially implemented instructions that never quite saw the light of day. A few seem to provide remarkably godlike powers that appear to circumvent on-chip security or even to rewrite the chip’s internal microcode.