CHAPTER 13

CD/DVD Drives and Specifications Chapter 13
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This is preferable because ATA does not share the single channel well and would cause a hard disk
drive to wait for CD/DVD commands to complete and vice versa. SCSI does not have this problem
because a SCSI host adapter can send commands to different devices without having to wait for each
previous command to complete.
The ATA interface represents the most cost-effective and high-performance interface for CD-ROM
drives. Most new systems that include a CD and/or DVD drive have it connected through ATA. You
can connect up to two drives to the secondary ATA connector; for more than that, SCSI is your only
choice and provides better performance as well.
Many systems on the market today can use the ATA/ATAPI CD/DVD drive as a bootable device, which
allows the vendor to supply a recovery CD that can restore the computer’s software to its factoryshipped
condition. Later, you’ll see how bootable CDs differ from ordinary CDs and how you can use
low-cost CD-R/CD-RW drives, along with mastering and imaging software to make your own bootable
CDs with your own preferred configuration.
√√ See “An Overview of the IDE Interface,” p. 476.
◊◊ See “Creating a Bootable Floppy with CD-ROM Support,” p. 772.
Parallel Port
Rather than opening the case to insert a SCSI adapter or connect an internal drive, you can install
some CD-ROM drives simply by connecting a cable to the PC’s parallel port and loading the appropriate
software. Although parallel port drives have been available for some time now, USB has for the
most part replaced the parallel port for this type of use.
Obviously, the advantages of CD-ROMs that use the parallel port interface are their ease of installation
and their portability. In an office environment where the primary function of CD-ROMs is to
install software, you can easily move one parallel port drive from machine to machine, rather than
purchase a drive for each system. If you use an operating system that supports Plug and Play (PnP),
such as Windows 9x, simply plugging a PnP drive into the parallel port causes the OS to detect the
new hardware and load the appropriate driver for you automatically.
For best performance, it’s recommended that you set your printer port to use IEEE-1284 standards,
such as ECP/EPP or ECP, before connecting your parallel-port CD-ROM. These are bidirectional, highspeed
extensions to the standard Centronics parallel port standard and provide better performance for
virtually any recent parallel device. These devices include printers, tape backups, and Zip and LS-120
drives (also known as SuperDrives), as well as CD-ROM, CD-R, and CD-RW drives.
Using the IEEE-1284 enhanced settings can make a tremendous difference in parallel-port CD-
ROM performance. For example, bidirectional (PS/2 style) can achieve data transfer rates of
100KB/sec–530KB/second, whereas EPP can achieve rates of about 1,200KB/second—12 times
that of standard (unidirectional).
◊◊ See “IEEE 1284 Parallel Port Standard,” p. 934.
Note
Parallel port CD-ROM drives nearly always include a cable with a pass-through connector. This connector plugs into the
parallel port and, if necessary, a printer cable can plug into the connector. This enables you to continue using the port to
connect to your printer while sharing the interface with the CD-ROM drive. Note there might be performance problems
when trying to print and read from the drive at the same time.