As mentioned above, each IDE channel can support two devices, hard disks or CD-ROMs. For optimal performance it is recommend that you use only one device per channel. If on the other hand, saving an IRQ is more of a priority than optimal performance then you may rearrange your setup and put both devices on the primary channel, and disable the secondary channel.
If you are using only the primary IDE channel on a system having a motherboard that contains two built-in controllers, then it is a must that you disable the secondary controller to free up the resources it uses. This is done by entering into the BIOS setup and looking in for the settings that control the IDE controllers, which are usually located in the "Integrated Peripherals" grouping. Once you locate this, disable the secondary IDE controller. You can refer to the settings indicated in the motherboard manual provided by the manufacturer.
