DOS ain't dead

I read the KBFR source code and:
MOV AX,0F000h
MOV ES,AX
MOV AL,ES:[0FFFEh]
CMP AL,0FCh ; AT BIOS ?
JZ @F
^^
Wrong! It should be JNA, because you should be testing if the model code is equal to *or below* FCh.

> Wrong! It should be JNA, because you should be testing if the model code is
> equal to *or below* FCh.
you are right, but it should rely on

INT 15 - SYSTEM - GET CONFIGURATION (XT >1986/1/10,AT mdl 3x9,CONV,XT286,PS)
AH = C0h

instead.