In the SCAS/CMPS annotated microcode, the path with the R DS microinstruction is for CMPS, not SCAS. SCAS compares AX against [ES:DI] while CMPS compares [DS:S

In the SCAS/CMPS annotated microcode, the path with the R DS microinstruction is for CMPS, not SCAS. SCAS compares AX against [ES:DI] while CMPS compares [DS:SI] against [ES:DI], so the paragraph before is slightly incorrect (should be "SCAS compares against the character in the accumulator, while CMPS reads the comparison character from SI").