Origin of "partition" in storage devices

[Paul Koning]

> On Feb 1, 2022, at 12:21 PM, Paul Koning via cctalk <cctalk at classiccmp.org> wrote:
> 
>> On Feb 1, 2022, at 12:16 PM, Mike Katz via cctalk <cctalk at classiccmp.org> wrote:
>> 
>> In the rotating drive world there is constant linear velocity (CLV) and constant angular velocity (CAV) drives.
>> 
>> On CLV drives the speed of rotation would vary based on the track (slower in the inner tracks and faster on the outer tracks).  This meant that the data rate and number of bits/track remained constant.
> 
> Slower on the outer tracks, I believe.  CDs work this way.

I suspect CLV was invented for CDs, in fact.  The reason is obvious: CDs contain uncompressed digital audio, i.e., constant bit rate.  If you want to avoid big buffers -- an expensive thing to have in 1980s consumer electronics -- the bits have to come off the media at essentially the desired payload data rate.  So you either use CAV with constant sector counts, which wastes a whole lot of capacity given that the ratio of inner to outer radius is quite large on a CD, or you go to CLV.  The variable rotation rate is easy enough to handle because CDs are accessed sequentially; the speed change on track switch is small because track switches are only by +1 (during play).

You can often hear the RPM changes clearly, if you're asking the CD player to do random access by skipping around the songs.

	paul