INT 10 - VIDEO - ALTERNATE FUNCTION SELECT (PS, EGA, VGA, MCGA) - GET EGA INFO
        AH = 12h
        BL = 10h
Return: BH = 00h color mode in effect (I/O port 3Dxh)
             01h mono mode in effect (I/O port 3Bxh)
        BL = installed memory (00h = 64K, 01h = 128K, 02h = 192K, 03h = 256K)
        CH = feature bits
        CL = switch settings
            bit 0: switch 1 OFF
            bit 1: switch 2 OFF
            bit 2: switch 3 OFF
            bit 3: switch 4 OFF
            bits 4-7: unused
Note:   one possible check for the presence of an EGA or later display card
          is to call this function with BH=FFh; if not present, BH will be
          unchanged on return

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