controllers

Short question, long answer. CDs/HDDs have "drive controllers" or a similar name as an integral part of the device itself. When most people think of controllers for HDDs/CDs, they are thinking about the IDE controller, that allows the pc to control the device, via a cable. IDE are 40-connector, flat cables. Now some PCs have the controller as part of the motherboard, whilst older pcs may have a controller card, that plugs into a slot on the motherboard, and has the cable to the devices plugged into it. Easiest way to find out is to follow the flat cable from the device. If it connects to a card plugged into the motherboard, that's the controller card. If t goes to a connector on the board itself, the board has an on-board controller.

Now to complicate the issue, some sound cards have an IDE connector that can be used to drive a CD; and there's another form of controller called SCSI which uses different controllers, cables and devices. Easy to recognise by the 50-way cable. Not compatible with IDE. Usually separate controllers, but some server motherboards have on-board SCSI controllers.

Hope this makes sense.
Bill