AT Attachment Packet Interface
The Enhanced IDE standard by itself works wonders for hooking up disk drives to PCs. But that's not enough. People want to attach tape drives and CD-ROMs to the same controller. Thanks to EIDE's support for the ATAPI standard, they can. Using ATAPI-capable hardware and software drivers, you can mix and match different types of drives on the same EIDE controller, which is both a convenience and a savings in hardware costs.
See also: EIDE