drive with read-only dip switch

Arno Wagner wrote in news:60ia0vF1qi80lU1@mid.individual.net
> 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.

And as we all know, SCSI drives are not HDDs.

>
> > 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,

(Yeah, obviously flashdrives do not use the ATA command set at all).
Any device that accepts write protect media will have extra code to
handle the extra functions that such a protection scheme requires.

> since the ''switch'' needs to understand the ATA command set.

Like that same effort isn't required for the physical drive itself when
fitted with such a switch.

>
> Arno

Robert Nichols wrote in news:fo3a4s$m17$1@omega-3a.local
> In article <60ia0vF1qi80lU1.TakeThisOut@mid.individual.net>,
> Arno Wagner <me.TakeThisOut@privacy.net> wrote:
> > Previously timeOday <timeOday-UNSPAM.TakeThisOut@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.