speed is stepped up. Early model recorders were CLV drives. The recording speed on such drives was rated in multiples of 150 KiB/s; a 4X drive, for instance, would write steadily at around 600 KiB/s. The transfer rate was kept constant by having the spindle motor in the drive vary in speed and run 2.4 times as fast when recording at the inner rim of the disc as on the outer rim. Some high-speed recorders use the zoned CLV method (ZCLV), which divides the disc into stepped zones, each of which has its own constant linear velocity. When the current zone is finished and the next zone is reached, the disc rotation will speed up, usually to the same angular speed as at the beginning of the previous zone. At higher speeds, ZCLV offers a compromise between CAV, which enables faster seek times, and CLV, which enables greater writing reliability. A ZCLV recorder rated at "52X", for example, would write at a 52X disc rpm on the innermost zone and then progressively step down to 20X disc rpm at the outer rim to keep the rate at which bits are recorded by the laser within a narrow range. This method is used for higher-speed CD-RW variants due to the narrow writing speed range of rewriteable media. Constant Angular Acceleration Constant Angular Acceleration (CAA) is a variant of CLV that is used on the Laserdisc format. The initial specification of CLV (as it applies to laserdisc) results in several playback artifacts to be present in the audio/video portion as well as compatibility problems with Laserdisc players as produced by different manufacturers. In the mid 1980s, Pioneer Electronics introduced the CAA scheme where the speed in rotation of the Laserdisc was lowered in steps and eliminated most playback artifacts and compatibility problems. Since its introduction, most manufacturers of Laserdiscs adopted the CAA format but still referred to their CAA-encoded product as CLV. See also Constant angular velocity (CAV) Zone bit recording (ZBR/ZCAV) Olivetti "personal computer" diskette format utilizing CLV with FM Sirius 1/Victor 9000 diskette format utilizing ZCLV, ZBR with GCR References Rotating disc computer storage media Audio storage Video storage Optical computer storage