Introduction; A New Type Of Drive; The Real Test - Toshiba ATAPI Installation Manual

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Introduction

Congratulations on the purchase of your Toshiba ATAPI CD-ROM drive. Read carefully

through this manual in order to install the drive and learn how to use it. For specification

details of your CD-ROM drive, see the accompanying specification booklet.

Early CD-ROM drives operated using CLV (Constant Linear Velocity) where the

amount of data passing under the read head was always constant. This meant that the

rotation speed varied depending on which part of the disk was being read - faster spin for

the inside of the disk and slower spin for the outside.

Your Toshiba CD-ROM drive uses advanced PCAV (Partial Constant Angular Velocity)

which fixes the rotation speed for some parts of the disk. The drive switches

automatically between CAV to achieve the fastest possible access times and CLV to

achieve the fastest possible sustained data transfer rate.

This means that the old designations of fixed rotation speed are less helpful with this

new type of CD-ROM drive - the disk spins at different speeds during different

processes.

Just spinning the disk faster does not necessarily mean the data is accessed or transferred

any faster. One of the reasons for this is that the laser head must be moved in and out

between the centre and the edge of the disk. The quality of the motor which moves the

laser head is vital as it must accelerate and then stop at exactly the right place on the disk

many thousands of times at incredible speeds.

The quality of the laser mechanism, on-board caching, error correction techniques, the

type of interface and the driver software can all have an effect on the access speed and

transfer rate. This means that a CD-ROM drive rated at a certain data transfer speed

might not really be able to achieve that speed because of bottlenecks elsewhere in the

drive

A drive with slow seek time, poor caching and poor error correction will cause

performance problems. Multimedia applications expect data to be delivered at an

acceptable rate. If the data is not delivered fast enough you notice a degradation in sound

or video quality while the computer waits for the next block of data from the CD-ROM

drive. Sometimes the poor data transfer speed can cause synchronisation between audio

and video material or between data and graphics to fail.

Introduction 3

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