On Thu, 12 Jul 2007 15:42:15 -0400, J R wrote: >>CD players, like the original Macintosh 390 K floppy disks, >>vary the angular velocity inversely with cylinder radius >>in order to have both uniform linear density and uniform >>data transfer rate. > >Right. But floppies and CDs don't revolve at 3000rpm >(or 7200rpm, whatever) like hard drives, so there are less >inertial challenges to overcome when varying the angular velocity.
A CD is also a primarily serially accessed device. Imagine the impact on seek time if the spin rate had to change at the same time. Besides, there is no reason to slow the drive when accessing the outer tracks as long as the electronics can keep up with the data rate. Today's drives are 10,000 and 15,000 RPM. At 550KB/track and 15,000 RPM data is being transferred at nearly 150 MB/second. Remember when 3 MB/second was considered to be fast? -- Tom Marchant ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
