)
Call EPP BIOS (Revision 7) entry point multiplexor functions with:
	DX = EPP port base I/O address
	AH = function
	    40h Query Mux
		Return: AH = status (see #00634)
			AL = currently-selected port
			CH = status flags
				bit 0: channel locked
				bit 1: interrupt pending
			BH destroyed
		Note:	the PhoenixBIOS v4.0 documentation lists BL as the
			  currently-selected port and AL as the status flags
	    41h Query Device Port
		AL = EPP multiplex device port (1-8)
		Return: AH = status (see #00634)
			CH = status flags (see #00638)
			BX = EPP product/device ID (0000h if undefined)
		Note:	the PhoenixBIOS v4.0 documentation lists AL as the
			  status flags and CX as the device ID
	    42h Set Product ID
		AL = EPP multiplex device port (1-8)
		CX = EPP product ID
		Return: AH = status (see #00634)
			BX destroyed
	    50h Query Daisy Chain
		AL = EPP multiplexor device port (1-8)
		Return: AH = status (see #00634)
			CH = status flags
				bit 0: channel locked
				bit 1: interrupt pending
			BL = currently-selected device
			BH = EPP daisy chain revision (high nybble = major)
			CL = daisy-chain depth (00h if no daisy chain)
			ES:DI -> ASCIZ driver vendor identification string
		Note:	the PhoenixBIOS v4.0 documentation lists AH=51h as
			  "Query Daisy Chain" and BL as the multiplexor port;
			  it also lists AL as status flags on return
	    51h Rescan Daisy Chain (dynamically reassign port numbers)
		AL = EPP multiplexor device port (1-8)
		Return: AH = status (see #00634)
			BX destroyed
		Note:	the PhoenixBIOS v4.0 documentation lists AH=50h as
			  "Rescan Daisy Chain" and BL as the multiplexor port
Notes:	these functions are only valid if a port multiplexor or daisy chain
	  is present
	PhoenixBIOS 4.0 documents function 50h as "Rescan" and 51h as
	  "Query Daisy Chain"
SeeAlso: #00632,INT 2D/AL=DCh