Int 1A Fn B10B  - Pci Bios V2.0c+ - Write Configuration Byte               [X]

   AX = B10Bh
   BH = bus number
   BL = device/function number (bits 7-3 device, bits 2-0 function)
   DI = register number (0000h-00FFh)
   CL = byte to write

Return: CF clear if successful
   CF set on error
   AH = status (00h,87h) (see #0653)
   EAX, EBX, ECX, and EDX may be modified
   all other flags (except IF) may be modified

Notes: this function may require up to 1024 byte of stack; it will not enable
     interrupts if they were disabled before making the call
   the meanings of BL and BH on entry were exchanged between the initial
     drafts of the specification and final implementation

See Also: AX=B108h,AX=B10Ch,AX=B10Dh,AX=B18Bh,INT 2F/AX=1684h/BX=304Ch