Reverse-engineering the register codes for the 8086 processor's microcode
The fixed-width microcode instructions with 5-bit register fields is very reminiscent of a classic RISC. It looks like the concept of breaking down instructions into RISC-like uops into was there since the beginning, but Intel only started marketing it that way with the Pentium.<p>It&#x27;s worth noting that, had the mapping from segment registers to internal register numbers included i5, it would&#x27;ve been possible to access several of the other internal registers with undocumented instructions.