Once upon a time I used an Emulex QD21, but I sold it because the actual
ESDI disks I had were a pain in the butt. Always crashing.
I still have a Webster (quad board) SRQD something.
I think I had a Dilog board also. It's been a while, probably 20 years.
On 4/18/2022 9:12 PM, Chris Zach via cctech wrote:
Interesting, what kind of ESDI controllers do you have? They got
advanced features like cache, ordered seeks, and burst mode/block mode
On 4/18/2022 6:09 PM, Douglas Taylor via cctech wrote:
Because of this I'm holding on to my DEC Qbus ESDI controllers!!!
You never know....
On 4/17/2022 4:35 PM, Guy Sotomayor via cctech wrote:
I chose ESDI and SMD fundamentally because the interface is 100%
digital (e.g. the data/clock separator is in the drive itself). So I
don't need to do any oversampling.
TTFN - Guy
On 4/17/22 11:12, Paul Koning via cctalk wrote:
On Apr 17, 2022, at 1:28 PM, shadoooo via cctalk
For reading a disk, an attractive approach is to do a high speed
analog capture of the waveforms. That way you don't need a priori
knowledge of the encoding, and it also allows you to use
sophisticated algorithms (DSP, digital filtering, etc.) to recover
marginal media. A number of old tape recovery projects have used
this approach. For disk you have to go faster if you use an
existing drive, but the numbers are perfectly manageable with
there's much discussion about the right method to transfer data
in and out.
Of course there are several methods, the right one must be
carefully chosen after some review of all the disk interfaces that
must be supported. The idea of having a copy of the whole disk in
RAM is OK, assuming that a maximum size of around 512MB is
required, as the RAM is also needed for the OS, and for Zynq
maximum is 1GB.
If you use this technique, you do generate a whole lot more data
than the formatted capacity of the drive; 10x to 100x or so. Throw
in another order of magnitude if you step across the surface in
small increments to avoid having to identify the track centerline
in advance -- again, somewhat like the tape recovery machines that
use a 36 track head to read 7 or 9 or 10 track tapes.
Fred mentioned how life gets hard if you don't have a drive. I'm
wondering how difficult it would be to build a useable "spin
table", basically an accurate spindle that will accept the pack to
be recovered and that will rotate at a modest speed, with a head
positioner that can accurately position a read head along the
surface. One head would suffice, RAMAC fashion. For slow rotation
you'd want an MR head, and perhaps supplied air to float the head
off the surface. Perhaps a scheme like this with slow rotation
could allow for recovery much of the data on a platter that
suffered a head crash, because you could spin it slowly enough that
either the head doesn't touch the scratched areas, or touches it
slowly enough that no further damage results.