INT 1A - PCI BIOS(Basic Input/Output System) A set of standardized calls giving low-level access to the hardware.  The BIOS is the lowest software layer above the actual hardware and serves to insulate programs (and operating systems) which use it from the details of accessing the hardware directly. v2.0c+ - WRITE CONFIGURATION BYTE
	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 #00729)
	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
SeeAlso: AX=B108h,AX=B10Ch,AX=B10Dh,AX=B18Bh,INT 2F/AX=1684h/BX=304Ch