INT 15 - later PSIBM PS/2, any model/2s - QUERY BOOT REFERENCE PARTITION
	AX = D602h
Return: CF clear on success
	    AH = 00h
	    AL = status of reference-partition boot request
		00h boot not requested
		01h boot requested
	CF set on error
	    AH = status (86h for function not supported)
SeeAlso: AX=D601h/BL=00h