Reading ESDI disks

Nigel Johnson nw.johnson at
Thu Feb 11 11:40:56 CST 2021

Doesn't ATA transfer the data in parallel?  ESDI uses the same two
connectors as MFM (20/36 IIRC) , and transfers the data serially.  The
difference between MFM and ESDI is that MFM transfers the raw analogue
data over the cable but ESDI transfers digital serial data.

Amateur Radio, the origin of the open-source concept!
Skype:  TILBURY2591 nw.johnson at

On 2021-02-11 12:36 p.m., Chuck Guzis via cctalk wrote:
> On 2/11/21 9:25 AM, Mattis Lind via cctalk wrote:
>> What is the best way of dumping the contents of an ESDI disk?
>> 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.
>> Is there any other way of dumping the disk contents?
>> In theory it should be just a matter of clocking the raw data and finding
>> the marks and extracting the data. Has anyone done something similar?
> I'm a little confused on this.  An ESDI drive, in my experience, behaves
> exactly like an ATA one, right down to the command set.   ESDI drives
> can be soft-or-hard sectored.
> What am I missing?
> --Chuck

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