if you want the code for this, it is quite simple:
Code:
MOV AX, 0xF000 ; set all the high bits to 1
PUSHF ; save state of flags register before modifying
PUSH AX
POPF ; move AX into FLAGS
PUSHF
POP AX ; move it back -- anything in flags forced to a specific value is changed
POPF ; restore previous flags
AND AH,0xF0 ; mask out the bottom part, and move it into flags for checking
JS no386 ; the sign bit is only set on 8086/8
JZ no386 ; bits 12:15 0 on start, and cannot be changed in RMode on 286,
; but can on 386
:386code ; if you get here you have a 386
standard disclaimer:
this code is public domain, and can be used by anyone for any reason, and modified in any way -- im not responsible for any problems with this code