On Thu, 11 Feb 2021, Chuck Guzis via cctalk wrote:
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?
I'm more than a LITTLE confused by parts of this discussion.
To what extent are ESDI controllers interchangeable with already written
drives?
Remember that XT/5160 ST506/412 controllers were often NOT
interchangeable, although AT/5170 ones usually were.
Mattis says that he has the controller that that drive was written with.
Some folks are talking about how the controller talks to the drive. If
using OS or BIOS (mine had a ROM), unless changing THAT, such as trying to
use a flux-transition device, controller to drive communication seems
largely irrelevant.
At least in the case of ISA, for the sake of compatibility, and
transition, the controller and drive COMBINATION looks the same to the
computer/OS as an ST506/412.
Similarly, on PCs, IDE typically, for the sake of compatibility, and
transition, the controller and drive COMBINATION looks the same to the
computer/OS as an ST506/412.
Similarly, on PCs, ATA typically, for the sake of compatibility, and
transition, the controller and drive COMBINATION looks the same to the
computer/OS as an ST506/412.
All followed the ST506/412, and strived for transparent compatibility,
but did not necessarily derive from each other.
