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Date:      Tue, 7 Mar 95 9:57:19 MST
From:      terry@cs.weber.edu (Terry Lambert)
To:        jmrueda@diatel.upm.es (Javier Martin Rueda)
Cc:        questions@FreeBSD.org
Subject:   Re: System hangs when changing root device
Message-ID:  <9503071657.AA24832@cs.weber.edu>
In-Reply-To: <629*/S=jmrueda/OU=diatel/O=upm/PRMD=iris/ADMD=mensatex/C=es/@MHS> from "Javier Martin Rueda" at Mar 7, 95 01:15:20 pm

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> > I created a boot disk with rawrite (using the "newer" bootdisk from FreeBSD
> > 2.0-RELEASE) and everything was probed OK, but after the message "changing
> > root device to fd0c" appeared, the computer freezed.
> 
> This is just to say that I changed the motherboard from a PCI+VESA with UMC
> chipset to a PCI+VESA with Opti chipset, and things started to work.
> 
> However, then the network card (SMC EtherPower 8432BT PCI) did not work.
> This was solved by changing the IRQ from 9 to 11. The computer also has
> a serial port in IRQ2, and that must be conflicting with IRQ9.
> 
> Maybe the problem with the old motherboard was also due to some IRQ
> conflict, although everything seemed to be probed OK. I must say that I
> have a VESA motherboard with UMC chipset at home and it works fine with
> FreeBSD 2.0R.

There are/were known cache writeback problems with the UMC chipset.

In theory, these are repairable using CMOS settings.  I believe the
interesting setting had to do with write-through vs. write-back.  I
thought this had been fixed in software and foolishly discarded the
information (well, put it on tape some place -- I never delete anything
I once found interesting, really).

If you could try this with your board and, if it fixed the problem,
document it for others, you would be well loved.


					Terry Lambert
					terry@cs.weber.edu
---
Any opinions in this posting are my own and not those of my present
or previous employers.



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