CDROMs on the other hand were originally designed to play music sequentially and are recorded at fixed data density -- Constant Linear Velocity. This requires the drive to vary its speed during read. While this results in more data stored per unit of surface area, it requires the drive to change rotation speed when moving to a different track. This results in lengthy seek times when CDROMs are read randomly since the drive must speed up or slow down. Some "Fast" CDROMs use CAV playback resulting in faster seeking, but in variable read rates -- slowest on the inner tracks where data is most likely to be recorded, and fastest on the outer tracks where data may well not be recorded. Quoted speeds for CAV CDROMs are for the faster outside tracks.
Return To Index Copyright 1994-2008 by Donald Kenney.