INT 16 U - PCIBM PC Tools v5.1-8.0 DESKTOP - GET/SET???
	AX = FFB8h
	BH = subfunction
	    00h get
		Return: BL = old value of ???
			CL = old value of ??? (v6.0+)
			CH = old value of ??? (v6.0+)
	    nonzero set
		BL = new value for ???
		CL = new value for ??? (v6.0+)
		CH = new value for ??? (v6.0+)
		DH = ???
		Return: AL = old value replaced by CL (v6.0+)
			AH = old value replaced by CH (v6.0+)