floppy disk controller broken

[Jeremy Chadwick]

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
> them?

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 |
| Parodius Networking                       http://www.parodius.com/ |
| UNIX Systems Administrator                  Mountain View, CA, USA |
| Making life hard for others since 1977.              PGP: 4BD6C0CB |