INT 15 - newer PS/2; various BIOSes - GET CPU TYPE AND MASK REVISION
        AH = C9h
        AL = 10h (may be required on some non-PS BIOSes)
Return: CF clear if successful
            AH = 00h
            CH = CPU type
                03h 80386DX or clone
                04h 80486
                23h 80386SX or clone
            CL = mask revision (stepping level)
                80386:
                    03h B1
                    05h D0
                    08h D1/D2/E1
                80386SX:
                    04h A0
                    05h B
                    08h C/D1
        CF set on error
            AH = status (80h,86h = function not supported)
Notes:  the BIOS must save DX at startup in order to be able to support this
          call; PS/2 Models 56, 57, 90, and 95 are known to support it
        the PS/2 BIOS merely reads CMOS locations 190h (type) and 191h (rev)

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