1 Feb
2022
1 Feb
'22
9:33 a.m.
On Feb 1, 2022, at 12:21 PM, Paul Koning via cctalk
<cctalk at classiccmp.org> wrote:
More precisely:
CLV means slower rotation when positioned on the outer cylinders. The outer cylinders
have more sectors; the layout is such that the linear bit density is roughly constant,
which in turn because of the constant linear velocity means constant data rate.
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.