Sys V/AT strange floppy problem

[Dick Dunn]

In article <11944 at grebyn.COM>, johnk at grebyn.COM (John Kennedy) writes:
> I've been experiencing a bizarre problem with a Sys V/AT that
> is no longer able to read or write floppies.  Everything works
> fine under MS-DOS, but not under unix...
...
> Software is:
> 	Sys V/AT, ver 2.3 installed on hard drive.
(etc.)

I've seen bizarre problems under V/AT 2.2 on my machine at home.  I had
pretty much decided that Microport was programming the floppy controller
wrong somehow, and it had something to do with formatting, because I could
use the machine's drive to format/read/write floppies under MS/DOS and
another UNIX, and to move floppies to/from the machine, but had a
consistent class of troubles with Microport.  Specifically, >>I could only
read a floppy under Microport if it had been formatted under Microport.<<
All other non-Microport combinations worked.  One of the notable failures
was to format and write a floppy under MS/DOS, then be unable to read it
under Microport on the same machine!

I also found that I would get repeatable errors on some floppies--as if
they were solidly bad--under Microport, yet I could use the floppies with
nary a complaint under other systems on the same machine.  I'm at a loss to
explain this sort of behavior *except* as a driver problem.  It's as if the
driver is doing something to get out in the margins.

> 1 - Format (floppies) works with no displayed errors.  Does this mean that 
>     it was successful or that errors aren't reported?

There are very few things that cause a format to report an error.  In par-
ticular, there's no verification that the formatting actually happened.

> 3 - Both 1.2 MB and 360 KB floppies get the errors.

Beware that you cannot dependably *write* a 360 Kb floppy in a 1.2 Mb
drive.  That's a matter of hardware; it's not *supposed* to work even
though it sometimes does.  You can read them, though.  If you've got a 1.2
Mb drive, you should be using HD floppies (*not* DD), formatting them in
high density (80 tracks * 2 sides), and writing in high density.

> 1 - Booting the uport boot floppy, either sys VAT 2.3 or 2.4 yields
>     "panic - cannot mount root".

This (and some other comments) says that you've got hardware problems.
Microport's problems with floppies may be making it worse, but there's
something else going on.
-- 
Dick Dunn      UUCP: {ncar,nbires}!ico!rcd           (303)449-2870
   ...Relax...don't worry...have a homebrew.