Some CD-ROM manufacturers provide a proprietary adapter board made specifically for their product. These boards are supplied with the drive and are not usually interchangeable. The early CD-ROM drives used either SCSI or a special version of a parallel port. Most modern CD-ROM devices are either IDE or SCSI.
Sound Cards with CD-ROM Interface
Many add-on sound cards have built-in CD-ROM controllers. Most sound cards come with a 15-pin female connector known as the MIDI (Musical Instrument Digital Interface) connector. Some of the newer cards come with a SCSI interface. Sound cards with the built-in controller interface were very useful for earlier computers that did not have a controller available on the motherboard. Because today's motherboards have the ability to connect four IDE devices, a sound card with a controller is generally not required.
If you purchase a sound card with a controller and you already have a CD-ROM drive installed, be sure to disable the controller on the sound card. This will prevent IRQ (interrupt request) and other potential conflicts.
SCSI Host Adapter
The SCSI interface is the most advanced CD-ROM interface and often operates at higher data transfer rates than other interfaces. A single card can handle both internal and external drives, including CD-ROM and other optical devices. A detailed discussion of SCSI drives is found later in Lesson 3: SCSI Drives. A SCSI CD-ROM drive can be installed in any SCSI chain. You can purchase SCSI adapters that connect directly to a parallel port on the computer.
New computers have primary and secondary IDE connectors as part of the motherboard and BIOS setup. It is becoming commonplace to install CD-ROM drives on the secondary controller.