floppy disk controller broken
koitsu at FreeBSD.org
Fri Sep 19 12:36:02 UTC 2008
On Fri, Sep 19, 2008 at 11:55:05AM +0200, Oliver Fromme wrote:
> Michel Talon wrote:
> > Oliver Fromme wrote:
> > > Michel Talon wrote:
> > > > Moreover, trying to write to the floppy:
> > > > niobe# dd if=/dev/zero of=/dev/fd0 conv=noerror
> > > > dd: /dev/fd0: Input/output error
> > > > 5+0 records in
> > > > 4+0 records out
> > > > 2048 bytes transferred in 4.054404 secs (505 bytes/sec)
> > > >
> > > > I don't expect such result. Traditionnally writing works, while reading
> > > > may fail.
> > >
> > > Maybe I misunderstand what you're saying, but ...
> > > When I try to write to a floppy that has *not* been
> > > successfully formatted, I very much expect to get
> > > Input/output error. Anything else would be a bug.
> > The floppy has certainly be formatted, in the past. Perhaps i
> > remember badly, i have not used floppies since years, but
> > in this case the behavior with Windows, Linux and ancient FreeBSD
> > was that you could write to the floppy, but could encounter errors
> > while reading.
> Since you mentioned "ancient" FreeBSD, I assume that was
> using buffered block devices, when FreeBSD still supported
That sounds right -- again, if my memory hasn't failed me...
> Nowadays /dev/fd0 is a character device which is
> unbuffered, i.e. your dd(1) command goes straight to the
> disk, and if the drive reports an error (typically sync
> mark not found if the floppy is unformatted), it goes back
> up to dd(1) immediately and you get Input/output error.
Ah ha! Evolution has occurred. Thanks for educating me. :-)
| Jeremy Chadwick jdc at parodius.com |
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