PC Hardware in a Nutshell, 3rd Edition

ATA Multichannel Support

The original ATA specification defined one dual-channel ATA interface that supported one or two ATA devices. ATA-2 defines a second interface, with the primary interface using standard ATA IRQ and base address, and the secondary interface using the alternate IRQ and base address that had always been set aside for that purpose. Any modern motherboard or interface card provides dual-ported ATA support.

Windows 9X/NT/2000/XP and Linux recognize and use the secondary interface automatically. DOS and 16-bit Windows are not dual-port ATA-aware, so installing more than two ATA drives with these operating systems requires either BIOS support for the secondary port or supplemental drivers. If BIOS Setup allows you to enter drive parameters for four drives, you already have the BIOS support you need. If BIOS Setup lists only two drives, you must (in order of desirability) install an updated system BIOS or use a dual-ported bus-mastering ATA adapter with an onboard dual-port BIOS or install dual-port device drivers.

In addition to the well-standardized primary and secondary ATA interfaces, some devices support semistandard tertiary and quaternary ATA interfaces. In theory, at least, you can support up to eight ATA devices on one computer by adding a dual-ported interface card that can be configured as tertiary/quaternary to a system that includes a standard dual-ported ATA interface, assuming that you have the four IRQs needed to support all four ports. We have not ...