Sys V/AT strange floppy problem

[John Kennedy]

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.  This is starting to become
a serious problem, as I am not able to back up the system.

Just wondering if anyone else has had any similar problems.

Hardware is:

    16-Mhz 286, 2 meg 80 ns memory.
	40 MB ST-251-1 hard drive
    1.2 MB floppy drive
    360 KB floppy drive
    misc serial ports, monitor, etc.

Software is:
	
	Sys V/AT, ver 2.3 installed on hard drive.
                     - or -
	Sys V/AT, ver 2.3 booted from uport boot floppy.
                     - or -
	Sys V/AT, ver 2.4 booted from uport boot floppy.


Symptoms are (from hard disk):

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

2 - Any read or write (cpio, dd) yields I/O errors.

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

(from boot floppy)

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



I have ruled out any patches to the kernel for serial ports, interrupts,
etc, as a problem exists in booting the distribution floppies.

I have tried removing all hardware except the disk controllers and 
CRT controllers, and the problems persist.

At this point, the disk drives and controller cards have been replaced.  I am 
beginning to suspect something on the mother board, having to do with
DMA transfers, or some other feature that uport utilizes, that DOS doesn't.

Am looking for any insights as to what features of the hardware uport 
utilizes, that DOS doesn't.  

The only other next step for me is to replace the mother board, but
I would really like to what's going on.

Thanks in advance for any insights,

John

-- 
John Kennedy            |        Second Source, Inc.
johnk at opel.UUCP         |        Annapolis, MD