DVD-ROM interfaces.

DVD-ROM drives connect to your computer via an EIDE, SCSI, or ATAPI interface. Which interface you choose to use depends upon the value you place on speed, ease of setup, expandability, and whether you go with an external or an internal drive.  Most internal drives use the EIDE or ATAPI interface, whereas external drives typically use a SCSI interface.

The EIDE (Enhanced IDE) interface is found on most PCs today.  It has a throughput of 13MB/sec and can run up to four devices. Older IDE systems can be upgraded to support EIDE.

ATAPI (AT Attachment Packet Interface) defines the IDE standard for CD-ROM drives, tape drives and now DVD drives.

SCSI interfaces are found on all Macintosh machines and on many of today's PCs.   It's relatively fast throughput speed -- 5MB/sec -- is ideal for accessing data from CD-ROM and DVD drives.

IDE interfaces with a throughput speed of 2MB/sec, can be found on most older PCs. But IDE only supports two hard drives at one time, and no other devices.  Therefore, IDE DVD-ROM drives come with ATAPI (AT Attachment Packet Interface) drivers which let the IDE interface interact with the DVD-ROM drive.