1 Feb
2022
1 Feb
'22
9:21 a.m.
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.
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