Reading ESDI disks

Mattis Lind mattislind at
Thu Feb 11 14:31:48 CST 2021

Den tors 11 feb. 2021 kl 20:36 skrev Fred Cisin via cctalk <
cctalk at>:

> On Thu, 11 Feb 2021, Mattis Lind via cctalk wrote:
> > What is the best way of dumping the contents of an ESDI disk?
> Same as for ST506/412

I usually use David Gessweins MFM emulator for dumping unknown MFM disks.
It works perfectly!

> > I have an original IBM Enhanced ESDI ISA controller board. Could that be
> > used under Linux? Or NetBSD/FreeNSD? I googled but didn't find much.
> Do you have suitable drivers?
> Yes, ESDI has been used with Linux.
> In some cases, probably including the IBM ESDI controller, it looks
> similar to the computer as an ST506/412 setup.
> Start with another drive, and get your controller, drive, and OS working
> with each other as ordinary drive, BEFORE trying to read an alien disk
> using them.  It is generally important to isolate variables, so that you
> can determine whether problems are your setup or are problems with the
> alien drive.
> > Is there any other way of dumping the disk contents?
> IS IT THE SAME controller that the drive was written with??
> If so, no problem.
> If not, PROBLEMS.

The drive was written by the very same controller, yes. The controller was
in a IBM RT PC that had a battery explosion. The ESDI controller may have
survived along with the disk. So the question is there drivers for this
board in anything else then a RT PC?

Chuck is saying that the ESDI command set on the controller level is
identical to ST506 controllers.  Anyone with experience of the "IBM
Enhanced ESDI controller"?

I did a fair bit of googling but it didn't turn up much when it came to
Linux support. Of course,  if it is the same as the ST506 AT controller
then it should work out of the box.

But then I thought, perhaps this is a more generic problem. People having
ESDI drives (well, SMD as well I guess) that there is no controller
available for or could be made running due to drivers or whatever. So what
if those drives could be read anyway.

Interfacewise it shouldn't be that complex. One benefit of ESDI is that the
clock extraction has already been done, so it is mostly a question on
finding marks calculating CRC.


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