Int 2F Fn 4A10  - Smartdrv V4.20+ - Get/set Flush Before Prompt, Cd-rom S  [c]

   AX = 4A10h
   BX = 0008h
   DL = subfunction
       00h set
       DH = new states
           bit 0: flush before prompt
           bits 1-7 reserved
       01h get

       Return: DH = status flags
               bit 0: (v4.2+) flush before prompt
               bit 1: (v5.0+) CD-ROM caching support installed

Note:  v4.2 was an interim release to fix problems in the SMARTDRV included
     with MS-DOS 6.00; v5.00 is included with MS-DOS 6.2