In those cases the bits/inch changed to keep a constant data rate and
constant number of bits and sectors per track.
On 2/1/2022 11:21 AM, Paul Koning wrote:
On Feb 1, 2022, at 12:16 PM, Mike Katz via cctalk <cctalk@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.
On CAV drives the rotational speed of the drive doesn't change, this means that
the data rate and number of bits/track changes depending on the track.
It means that only if the sector count changes. That's true for modern drives and for
the CDC 6603; it wasn't true for quite a while. A lot of "classic" disk drives
have constant sector counts. So, for example, an RP06 is a CAV drive and its transfer
rate is independent of cylinder number since the sector count per track is constant.
I think hard drives are CAV as a rule because changing the spin rate as part of
a seek takes too long.
paul
