Unlike vinyl discs where the reading head (tone arm) moves along the "data spiral" with computer discs, hard drives and optical discs drives, the reading head usually follows a fixed path across the "data spiral". Therefore unlike vinyl where the disc is revolved at a constant speed, for computer discs the speed at which the head moves forward, or backwards is constant but the rotational speed increases or decreases depending on where the head is relative to the discs radius.
To achieve a, hopefully, constant data transfer rate between the disc and the pc; for hard discs, which usually have a "data spiral" that runs from the outside to the inside the rotational speed will decrease as the head advances towards the centre of the disc. For optical discs (cds and dvds), where the "data spiral" runs from the inside to outside, the rotational speed will increase as the head retreats towards the outside of the disc.
The "speed" quoted for Optical Disc Drives is it's Maximum Speed, the speed used to achieve a constant data transfer rate will usually vary.
Therefore, if either the software used to rip an optical disc, or the optical disc drive, consistently reports that it carried out that operation at the drives "maximum speed" start to panic because that should seldom happen!!!!
