The CD-ROM (compact disc read-only memory)
is a technology taken directly from the audio world that has
become standard equipment for computers. This guide covers the
basics of installing and using CD-ROM drives.
Advantages of CD-ROM Drives
If a hard disk drive holds more information
than a floppy disk drive, accesses the information faster,
and reads and writes information, then why do we need CD-ROM
drives? The answer is simple: a compact disc can hold large
amounts (650 MB) of removable data and can be mass-produced at a
very low cost.
The CD has become the medium of choice for
software distribution by manufacturers. DVD (digital video disc)
technology is beginning to replace traditional CD-ROM technology
on many new PCs, but DVD drives can read CD-ROM. It is
expected that CD-ROM will be a standard distribution method for
the foreseeable future.
An entire software package can be stored on
one CD. For example, the early versions of the Microsoft Office
Suite were supplied on 32 floppy disks. Today, the entire
program suite and its manuals are stored on a single CD. It is
also much faster to install a CD. The user simply starts it up,
enters any required information, and comes back later; it's no
longer necessary to feed disk after disk into the computer. When
they were introduced, CDs held large databases such as
encyclopedias. Today, they are used for every possible type of
data, from national phone directories and software libraries to
collections of clip art, music, and games. The following
table lists the advantages of storing data on a CD.
||Up to 650 MB
of data fit on a single 5-inch disc. (Smaller than the
original 5.25-inch floppy disk, a CD holds almost 2000
times as much information.)
||The CD is a
cannot be changed
||A CD is
read-only, which prevents accidental erasure of programs
than the standard 5.25-inch or 3.5-inch disks, CDs are
not magnetic media and thus are not subject to the same
dangers posed by proximity to electrical sources or
audio-capable, allowing special compression of audio,
image, and video data. They can be used to play standard
audio CDs and have the capacity to store and record
Development of the CD
The development of the computer CD roughly
paralleled the audio (music) CD:
- In 1979, the CD, as a storage medium,
was introduced in the audio industry.
- In 1985, the CD came to the computer
industry. Development was slow because the hardware was too
expensive for most manufacturers and users.
- In 1991, the CD-ROM/XA standard was
enhanced, and multimedia requirements for hardware were
- In 1993, high-quality video playback
came to the computer.
- Today, the price of CD-ROM drives
continues to drop, while their speed climbs. Approximately
85 percent of all computers include an internal CD-ROM drive
as standard equipment. Most software packages are shipped in
CD-ROM versions (3.5-inch disk versions are available but
usually only by special order, and often they do not contain
all the extras of the CD version).
About CD-ROM Standards
The CD-ROM world makes use of several
standards. These are usually referred to by the color of the
cover of the volume issued by the ISO (International
Organization for Standardization) committee—for example, the
White Book, Yellow Book, and so on. ISO formats are discussed in
more detail later in this guide.
CD-ROMs store data as a series of 1s and
0s, just like a floppy disk or a hard disk drive. However,
instead of using magnetic energy to read and write data, CD readers
and writers use laser energy. There are two major advantages to
- There is no physical contact between the
surface of the CD and the reading device.
- The diameter of the laser beam is so
small that storage tracks can be written very close
together, allowing more data to be stored in a smaller
Hard Disk Drives vs. CD-ROMs
With the cost of hard disk drives falling
and the amount of available data storage rising, the hard drive
is still king of the storage media. Optical data-storage devices
hold their place as removable media and as the media of choice
for archival data storage.
A CD platter is composed of a reflective
layer of aluminum applied to a synthetic base that is composed
of polymers. A layer of transparent polycarbonate covers the
aluminum. A protective coating of lacquer is applied to the
surface to protect it from dust, dirt, and scratches.
CD-recordable (CD-R) discs use
materials other than aluminum. They often have a yellow or
green cast on the data side. Not all CD-ROM readers are able
to read these discs—some older readers based on IDE
(Integrated Drive Electronics) are incompatible with CD-R
Data is written by creating pits and lands
on the CD's surface. A pit is a depression on the surface, and a
land is the height of the original surface. The transition from
a land to a pit, or a pit to a land, represents a binary
character of 1. Lands and pits represent binary 0. The reading
of data is based on timing—the speed at which the CD is
rotating—and the reflection of light. If no data is on the
disk, the reflectivity will not change and the CD will read a
series of binary 0s. There are approximately 4 to 5 million pits
per CD. They are arranged in a single outward-running spiral
(track) approximately 3.75 miles (6 kilometers) long. The
distance between each element is 1.6 thousandths of a
Connecting a CD-ROM Drive
A CD-ROM drive is a peripheral device and
must be connected to the bus of the computer through a
controller. There are several ways to install a CD-ROM drive.
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
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 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.
IDE / ATA
New computers have primary and secondary
IDE connectors as part of the motherboard and BIOS setup. It is
now commonplace to install CD-ROM drives on the secondary
Any CD-ROM drive that meets the Yellow Book
standards (created by the audio industry for sound and adopted
by the computer industry) has the ability to play back audio.
Most CD-ROM drives contain the circuitry and chips to convert
digital audio data into sound data. Most drives and sound cards
also have a headphone jack, as well as audio jacks to connect to
a stereo system. The only requirement is that the drive support
the ISO 9660 standard for the file system. ISO 9660 is also
known as the High Sierra Format. The ISO 9660 format is a
standard for writing data to a CD-ROM for use in a
cross-platform environment. This standard is compatible with
MS-DOS, Windows, UNIX, Macintosh, and other operating systems.
When purchasing or recommending a CD-ROM
drive, you need to consider two values. The first is data
transfer rate. The long-time standard for transfer rate has been
150 KB per second, and this is the basis for measuring CD-ROM
drives today. A 2X CD-ROM drive operates at 300 KB per second, a
4X at 600 KB per second, and so on. A typical CD-ROM drive today
will operate at 24X or 32X (4.8 MB per second) or faster. A hard
disk drive typically operates between 800 KB and 1.8 MB per
The second value to look at is the drive's
mean access time. This is the time it takes the head to move
over half the tracks. Typical access time is 200 to 400
milliseconds (ms). Today's CD-ROM drives can have faster data
transfer speeds than many hard drives, but their mean access
time is 20 or so times slower. This means that while a CD-ROM
drive will outperform the hard disk drive for copying or loading
a large chunk of contiguous data, it will be beaten by the hard
drive on random access tasks.
Although the transfer rate increases in
multiples, the mean access time does not. The following table
lists transfer rates and access speeds for some common CD-ROM
||600 KB per
||900 KB per
||1200 KB per
||1800 KB per
||2.4 MB per
||3.6 MB per
Installing a CD-ROM Drive
Installing a CD-ROM drive is a four-step
- Install the drive controller card, if
needed. Follow the instructions with the card.
- Install the CD-ROM drive in the computer
- Attach the data and power cables.
- Install the necessary drivers and set up
the CD-ROM drive.
The most difficult part of installing a
CD-ROM drive is determining which controller card is best for
the system. The controller card should be selected before buying
the CD-ROM drive because it must be compatible with both the
CD-ROM drive and the motherboard's expansion slot. There are
several ways to ensure this:
- Use the secondary IDE controller on the
- Install a new controller card (this
might be supplied with the CD-ROM drive).
- Install the CD-ROM drive in an existing
- Install a new SCSI host adapter and
create a new SCSI chain.
- Use an existing sound card with a CD-ROM
A quick review of how the computer is
currently equipped will guide you in the selection of the proper
card. In most cases, there will be a SCSI or IDE interface
available. Whatever card arrangement you choose, be sure to
disable any other possibly conflicting cards. Confirming the
extent of the computer's resources before purchasing a new
CD-ROM drive could save you the time and frustration of having
to return or exchange it.
Installing the Drive Internally
A CD-ROM drive can be mounted easily in any
computer that has an open bay for a 5.25-inch disk drive.
Physical installation is as simple as installing a floppy disk
drive. Most new CD-ROM drives come with a hardware kit, which
includes a combination of screws and brackets.
Make sure you have all the tools and parts
before beginning. These include:
- The CD-ROM drive.
- The correct cables.
- The appropriate hardware (including
special mounting rails for the PC's case).
- A flat-head screwdriver.
- A Phillips screwdriver.
- Needle-nose pliers or tweezers (for
Connecting the cables for a CD-ROM drive is
as simple as installing a floppy disk drive. There are two
cables—a flat ribbon cable (for data) and a power cable. Be
sure to connect the flat ribbon cable to the correct location on
both the controller and the CD-ROM drive (the red wire going to
pin 1). If there are no available power cables, use a Y power
splitter cable (this will split a single Molex connector
into two connectors. There might also be an audio out cable (two
to four wires) that connects to a sound card. This connection
will allow you to take full advantage of the audio capabilities
of the CD-ROM drive.
If you are adding an IDE-style CD-ROM
drive, be sure to set the master/slave jumper as required. For
SCSI drives, you must set the proper SCSI ID using either a
jumper or switch and make sure the chain is properly terminated.
The file structure for a CD-ROM drive is
different from the directory used by the MS-DOS FAT (file
allocation table). Therefore, a special driver is necessary for
MS-DOS to be able to recognize this device as a drive. A
standard device driver supplied by the manufacturer (for BIOS)
might also be required.
Microsoft's MSCDEX.EXE, an MS-DOS resident
application, provides the required translation and also
specifies the device driver required by the device. The
following changes in CONFIG.SYS and AUTOEXEC.BAT will do the
To ensure drive number assignment space,
type the following line. (Note that the last drive letter
assignment and, therefore, the number of drives, can be
limited by assigning a lower value letter).
- Add the following line to AUTOEXEC.BAT:
/d:mscd001 /l:e /m:10
This instruction provides the location of
the driver and any switches required to set up the driver. You
might have to consult the documentation for the CD-ROM drive to
determine which, if any, switches are required.
Many CD-ROM drive installation disks will
make these changes automatically.
Windows 95 and 98
Windows 95 and 98 use a 32-bit
protected-mode driver called VCDFSD.VXD. This driver replaced
MSCDEX.EXE, the MS-DOS real-mode driver. When adding a new
CD-ROM drive after Windows 95 has been installed, be sure to use
the Add New Hardware wizard. This wizard will properly identify
and set up the CD-ROM drive. With the Windows 95 and 98 Plug and
Play feature, installing a new CD-ROM drive is simple—the
operating system will recognize the drive and run the install
If you intend to use a CD-ROM
drive in the MS-DOS mode (from a bootable disk), the
real-mode drivers will have to be installed and added to the
CONFIG.SYS and AUTOEXEC.BAT files of the boot disk.
You can use a Windows 98 startup
disk to obtain the files required to recognize a CD-ROM
drive. Be sure that the PC has the proper software licenses
to use those files.
The term multimedia embraces a number of
computer technologies, but refers primarily to video, sound, and
the storage required by these large files. Basically, multimedia
is a combination of graphics, data, and sound on a computer. In
all practicality, the concept of adding multimedia simply means
adding and configuring a sound card, a video card, and a CD-ROM
drive to a system.
Microsoft formed an organization called the
Multimedia PC Marketing Council in 1991 to generate standards
for multimedia computers. The council created several multimedia
PC (MPC) standards, and it licenses its logo and trademark to manufacturers
whose hardware and software conform to these guidelines.
The Multimedia PC Marketing Council
formally transferred responsibility for its standards to
the Multimedia PC Working Group of the Software Publishers
Association (SPA). This group includes many of the same members
as the original MPC Marketing Council. The group's first
creation was a new MPC standard.
The MPC Marketing Council originally
developed two primary standards for multimedia: MPC Level 1 and
MPC Level 2. Under the direction of the SPA, the first two
standards have been replaced by a third, called MPC Level 3 (MPC
3), which SPA introduced in June 1995. (There are currently no
plans for the publication of any additional MPC standards.)
These standards define the minimum capabilities for a multimedia
computer. The following table presents these standards.
||16 MHz 386SX
||25 MHz 486SX
||1.44 MB 3.5-inch
||1.44 MB 3.5-inch
||1.44 MB 3.5-inch
|VGA video resolution
||640 x 480; 16 colors
||640 x 480; 64,000 colors
||640 x 480; 64,000 colors
||Serial; parallel; MIDI;
||Serial; parallel; MIDI;
||Serial; parallel; MIDI;
||Microsoft Windows 3.1
||Microsoft Windows 3.1
||Microsoft Windows 3.1
You should consider the MPC 3 specification
as the bare minimum for any multimedia system today.
Specifically, a recommended system exceeds the Level 3 standards
in several areas such as RAM, hard disk size, and video
capability. Note that although speakers are not technically part
of the MPC specification, sound reproduction does require
external speakers! The built-in speaker used for POST beep codes
is not sufficient for this quality of sound.
With the advent of multimedia computers and
software, manipulating full-motion video was the next logical
step. A modern high-speed multimedia computer has become
standard equipment in the moviemaking industry. Today, even
amateur filmmakers can use their computers to give home movies a
touch of professionalism.
Video-capture software provides an
interface that allows users to import and export video formats
in order to edit them with their computers. This software allows
a user to view audio waveforms and video images, create files,
capture single frame or full-motion video, and edit video clips
and still frames for content and effects.
File-editing functions such as zoom, undo,
cut, paste, crop, and clear can be used to edit audio and visual
files. Users can also set the compression controls to the type
of format desired and determine the capture rates. The capture
rate for full-motion video (equivalent to what you would find in
TV or on the big screen) is 30 frames per second (fps), but some
systems might not be able to reach this potential. Professional
systems include very large, very fast hard disk drives for data
buffering. A typical user of video-capture software might
realize a frame-capture rate of only up to 15 fps without adding
an arsenal of hardware to enhance the system.
Most new PCs will far exceed the
basic multimedia requirements listed above.
The following points summarize the main
elements of this guide:
- A CD-ROM drive is now a standard
component of a computer system.
- CD-ROM data transfer rates are based on
a factor of 150 KB per second.
- Installing a CD-ROM drive is as easy as
installing a floppy disk drive.
- The proper drivers must be loaded before
a CD-ROM drive can be accessed by the processor.
- To run a CD-ROM drive from MS-DOS, the
real-mode drivers must be loaded.
- A CD-ROM drive is an essential part of
the multimedia standard.
Copyright © The NOSPIN Group, Inc. 1991-2009. All