Comment by Polizeiposaune

Yep. The "high" registers as an alias for bits 8-15 of certain registers are one of many warts in the architecture; they should have been purged from 32-bit and 64-bit code, and left to rot in 16-bit mode only.

Intel blew it when they let them continue to work in to 32-bit code on the 386, and then AMD blew it when they repeated the mistake when defining the 64-bit ISA.