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On Tue, 7 Oct 1997, Mitchell Yee wrote: > > Does anyone have any idea what is an 8X-20X CAV CD-ROM drive? Check > http://www.us.pc.ibm.com/options/thinkmax1.html > > I need to add a CD-ROM to my 760XL and was ready to buy the 8X, but > maybe this drive does more? There are two part numbers listed: > 00K7903 or 11J8933 CAV is Constant Angular Velocity. Data on CDs are encoded with CLV, Constant Linear Velocity. That is, there is the same amount of data per inch of track. That means the CD player must slow down when reading from the outside tracks, and speed up when reading from the inside tracks - the amount of linear distance passing under the read laser goes as 2*pi*R. A CAV player spins at the same rate no matter where it's reading. This simplifies the spinning mechanism, but complicates the reading mechanism. When you read from an outside track, the data comes in faster (because there is more of it per revolution), and that would probably be the 20x. When you read from an inside track the data comes in slower (because there is less of it per revolution), and that is probably the 8x. That's my guess based on CAV/CLV from laserdiscs (only on those, CAV and CLV describe the way the data is actually encoded on the discs). -- John H. Kim kim@mak.com