CAV & CLV

Constant Angular Velocity refers to the rotational characteristic of the drive. In CAV mode, the rpm remains the same, so data closer to the outer margins of the CD are read or written faster than when present on the inner side. Most drives use this mode of operation when dealing with data nearer to the inner margin, and switch to CLV when closer to the outer margin. Constant Linear Velocity drives do not have a fixed rpm, but change this to allow the same length of track to be covered. This is made possible by using a higher rpm when reading areas close to the inner side, and using a lower rpm when reading data off the outer side.