; more source code at http://www.ahjoe.com/source/srcdown.asp

        PUBLIC  CPUTYPE

CODE    SEGMENT
        ASSUME  CS:CODE
CPUTYPE PROC    FAR
;OUT: AX=01, 8086; AX=02, 80286; AX=03, 80386; AX=04, 80486 UP;

        PUSH    BX

        PUSHF
        POP     AX
        MOV     BX, AX

        AND     AX, 0FFFH       ; CLEAR b15-b12
        PUSH    AX
        POPF
        PUSHF
        POP     AX
        AND     AH, 0F0H
        JNZ     IS8086

        MOV     AX, BX
        OR      AX, 0F000H      ; SET b15-b12
        PUSH    AX
        POPF
        PUSHF
        POP     AX
        AND     AH, 0F0H
        JZ      IS80286

        MOV     BX, SP
        AND     SP, NOT 3
        DB      66H
        PUSHF
        DB      66H
        POP     AX
        DB      66H
        OR      AX, 0
        DW      4
        DB      66H
        PUSH    AX
        DB      66H
        POPF
        DB      66H
        PUSHF
        DB      66H
        POP     AX
        DB      66H
        TEST    AX, 0
        DW      4
        JZ      IS80386
        JMP     IS80486

IS8086:
        MOV     AX, 01
        POP     BX
        RETF

IS80286:
        MOV     AX, 02
        POP     BX
        RETF

IS80386:
        MOV     AX, 03
        MOV     SP, BX
        POP     BX
        RETF

IS80486:
        DB      66H
        AND     AX, NOT 0
        DW      NOT 4
        DB      66H
        PUSH    AX
        DB      66H
        POPF
        MOV     AX, 04
        MOV     SP, BX
        POP     BX
        RETF
CPUTYPE ENDP

CODE    ENDS
        END     CPUTYPE