1 Feb
2022
1 Feb
'22
10:23 a.m.
On Feb 1, 2022, at 1:03 PM, Chuck Guzis via cctalk
<cctalk at classiccmp.org> wrote:
On 2/1/22 09:16, Mike Katz via cctalk wrote:
As far as I know zoned recording is universal at this point. Don't know how far back
it goes. Did any DEC MSCP disks use it?
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.
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.
I suspect that most recent ATA and SCSI drives employ "Zoned" recording.
That is, the disk is divided up into several annular "zones", each with
its own data rate. The rotational speed remains constant, however. This is not even recent. The old Bryant 4000 disks
used such a scheme
and it was used on many old drives after that.
Those are the ones CDC sold as 6603. Four zones, handled by the driver. (Also 12 bit
parallel data rather than the usual serial data stream.)
paul