An ordinary BUS has 3 sockets.1 is to be connected to motherboard and second to be connected to a device.What's the third one for? . I have a DVD RAM drive and a CD RW drive. my motherboard(845GV) has only IDE1 & 2.one is connected to HDD and another to DVD RAM drive. Can I use a single BUS to connect both of them(DVD RAM & CD RW)??