Re-Education
The Register expects plenty of OS developers are about to be sent to compulsory re-education sessions on the x86-64 architecture
The x86 architecture is so big and complex I'd be surprised if anyone knew it completely. The instruction set reference guide from Intel is over 2,000 pages long alone. And that's just one of the four volumes!
The more complex a device, the less likely you are to fully understand how it works and the easier it is to get it (horribly) wrong.