INT 10 - Everex Extended Video BIOS - RETURN EMULATION STATUS
        AX = 7000h
        BX = 0000h
Return: AL = 70h if Trident-based Everex card
        CL = monitor type
            00h mono
            01h CGA
            02h EGA
            03h digital multifrequency
            04h IBM PS/2
            05h IBM 8514
            06h SuperVGA
            07h analog multifrequency
            08h super multifrequency
        CH = feature bits
            bits 7,6: 00 = 256K memory
                      01 = 512K memory
                      10 = 1024K
                      11 = 2048K memory
            bit 5:    special oscillator present
            bit 4:    VGA protect enabled
            bit 0:    6845 emulation
        DX = video board info
            bits 4-15: board ID model
            bits 0-3:  board ID revision
        DI = BCD BIOS version number
Note:   board models for Trident-based Everex cards:
            236h Ultragraphics II
            620h Vision VGA
            673h EVGA
            678h Viewpoint