drive with read-only dip switch

Robert Nichols wrote in news:fo3a4s$m17$1@omega-3a.local
> In article <60ia0vF1qi80lU1.RemoveThis@mid.individual.net>,
> Arno Wagner <me.RemoveThis@privacy.net> wrote:
> > Previously timeOday <timeOday-UNSPAM.RemoveThis@theknack.net> wrote:
> > > Arno Wagner wrote:
> >
> > > > For drive manufactueres, spending the extra 50 Cent is not cost
> > > > effective, since apparently only very, very few people
> > > > want this feature.
> > > >
> > > > Arno
> >
> > > Floppy drives, Mini-DV, VHS, some flash drives, and audio tape all have
> > > write-protect switches.
> >
> > Indeed. But they are on removable media (counting the flash
> > drives as media). HDDs are not in that class.
> >
> > > If not on the drive itself, perhaps an external HDD enclosure could
> > > offer that feature.
> >
> > They could. Of course, implementing this is more diffecult for (S)ATA,
> > than for the removable medua you mention, since the ''switch''
> > needs to understand the ATA command set.
>
> That would be true for parallel ATA as well. Accessing and reading data
> from the drive requires writes to internal control registers.

> You can't just interrupt the "WRITE" signal in the bus and expect to
> use the drive at all.

Right,
but if you know through the other bus signals that a device register write
is underway you can interrupt conditionally using those other bussignals.

But that's all academic/besides the point.
The point being that you need a controller response back to the host
saying that the device cannot write.
Otherwise you can move data to the drive thinking you won't loose it because it will be saved there, but it just vanishes.
Same with saving hours of hard work into oblivian without any warnings.

Arno Wagner wrote in news:60luv9F1pornjU1@mid.individual.net
> Previously Robert Nichols <SEE_SIGNATURE.RemoveThis@localhost.localdomain.invalid> wrote:
> > In article <60ia0vF1qi80lU1.RemoveThis@mid.individual.net>,
> > Arno Wagner <me.RemoveThis@privacy.net> wrote:
> > > Previously timeOday <timeOday-UNSPAM.RemoveThis@theknack.net> wrote:
> > > > Arno Wagner wrote:
> > >
> > > > > For drive manufactueres, spending the extra 50 Cent is not cost
> > > > > effective, since apparently only very, very few people
> > > > > want this feature.
> > > > >
> > > > > Arno
> > >
> > > > Floppy drives, Mini-DV, VHS, some flash drives, and audio tape all have
> > > > write-protect switches.
> > >
> > > Indeed. But they are on removable media (counting the flash
> > > drives as media). HDDs are not in that class.
> > >
> > > > If not on the drive itself, perhaps an external HDD enclosure could
> > > > offer that feature.
> > >
> > > They could. Of course, implementing this is more diffecult for (S)ATA,
> > > than for the removable medua you mention, since the ''switch''
> > > needs to understand the ATA command set.
>
> > That would be true for parallel ATA as well.
>
> Have you seen the "(" and ")" around the "S" above?
>
> > Accessing and reading data
> > from the drive requires writes to internal control registers. You can't
> > just interrupt the "WRITE" signal in the bus and expect to use the drive
> > at all.

> Indeed.

> THat was feasible, though, with MFM and RLL drives.

Like that is all that is required.

>
> Arno