1 Feb
2022
1 Feb
'22
10 a.m.
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 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