Int 15 Fn D042  R - Intel Pentium Pro Bios Update - Bios Update Control    [-]

   AX = D042h
   BL = 02h
   BH = function
       01h enable update loading at initialization time
       02h check whether update loading is enabled
   CX,DX,SI = segments of three 64K scratchpad areas for BIOS use

Return: CF clear if successful
   CF set on error
   AH = status (see #0456)
       00h successful
       BL = enabled/disabled flag
       86h not implemented
   AL = OEM error (if AH is not 00h or 86h, otherwise undefined)
       00h successful

Notes: this API must be called from actual real mode, not V86 mode
   at least 32K stack space must be available when this function is called
   there is no call to disable update loading due to security risks; the
     BIOS setup can disable loading

See Also: AX=D042h/BL=00h,AX=D042h/BL=02h,AX=D042h/BL=03h