Configuring a single IDE/ATA or ATAPI device is very simple. One just needs to jumper it and then connect it with an IDE/ATA cable, and that's it. However, setting up more than one device is a little complicated. In some special cases, you just jumper pairs as master and slave or use cable select and use both the primary and secondary channels to get support for up to four devices.
It is not difficult setting up multiple devices. There are real performance reasons why it makes sense to put some thought into how one decides to allocate different drives to different IDE channels, and which one to make master and which slave.
Master/Slave Channel Sharing:
At a given point of time, each IDE/ATA channel can only deal with one request, to one device. One cannot even begin a second request, even to a different drive, until the first request is completed. This means that if two devices are put on the same channel, they must share it. In practical terms, this means that when at any point of time one device is in use, the other must remain silent. In contrast, two disks on two different IDE/ATA channels can process requests simultaneously on most motherboards. The bottom line is that the best way to configure multiple devices is to make each of them a single drive on its own channel.
