An Important Note Regarding Optical Drives ...

The first CD-ROM drives were capable of transferring data at speeds of 150KBps and were dubbed "single-speed" or "1X" drives. Therefore, a "40X" drive should theoretically be able to transfer data at speeds forty times that of a "1X" drive. Unfortunately, that is not the case.

“Max Variable” and CAV vs. CLV

CAV, short for Constant Angular Velocity, is a technique for accessing data off of rotating disks. With CAV, the disk rotates at a constant speed regardless of what area of the disk is being accessed. This differs from Constant Linear Velocity (CLV), which rotates the disk faster for inner tracks. This simply means that the drive adjusts the rotational speed to ensure that the throughput is constant from the inner track all the way through the outer track.

Due to the fact that many CD-ROM Drive manufacturers use CAV (or a hybrid CAV/CLV) when measuring the speed of their devices, you will actually encounter varying speeds from your CD-ROM drive, depending on whether the drive is reading the inside or the outside track of the disk. This is why BOLData now refers to all of these devices as, for example, “ ...40X Max Variable ...” drives. The “40X” is the maximum speed that the drive can achieve - when reading the outer edges of the compact disk only! The actual speed varies depending on what section of the disk is being read, hence the word variable.