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Best of the Newsgroups: panic trap bios checksum

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From: Bela Lubkin <belal@caldera.com>
Subject: Re: meaning of CheckSum: 0x02 * * Invalid * * in hw output ?
Date: Thu, 19 Dec 2002 22:28:15 GMT References: <862c810.0212180852.2a1e3b3a@posting.google.com>

Terry Paterson wrote:

> I have a server in the field which is occassionally panicing, with a
> k_trap (..00E )message.
> 
> we are trying to have the hardware checked out - running diagnostics
> on the RAM, etc ..
> 
> however - whilst looking around I spotted the following in the output
> from the hw command can anyone tell me what it means ? and does anyone
> have any thoughts as to what might be causing the panics ? there
> does'nt seem to be any obvious pattern - sometimes there is nobody
> logged-in, sometimes 1-2 hundred users, it has an Intel PRO100/B NIC
> which I seem to remember has had quite a few driver updates - so I
> might check that one out too.

My car doesn't work, do you have any ideas on why?  Not enough
information.

Panics often (not always) have an informational message before the
k_trap message; you should include that.  More importantly, there is
always a way to get information about _where_ in the kernel the panic
happened.  If a dump is written to disk, you can get kernel stack
tracebacks with any of `sysdump`, `scodb` or `crash`.  If not, you can
link scodb into the kernel and get an interactive traceback during a
panic.

>    Adapter BIOS ROM
>        Address:        0xc8000 - 0xc87ff
>        Size:           2Kb
>        CheckSum:       0x00  (As expected)
> 
>    Adapter BIOS ROM
>        Address:        0xc8800 - 0xcc7ff
>        Size:           16Kb
>        CheckSum:       0x02  * * Invalid * *
> 
>    System BIOS ROM
>        Address:        0xe0000 - 0xfffff
>        Size:           128Kb
>        BIOS Date:      05/17/01
>        BIOS Category:  IBM PC/XT-286
>        BIOS ID:        PhoenixBIOS 4.06.43 RK

OpenServer makes very little use of BIOS.  `hw` presents BIOS
information so that you'll know more about your machine, not because it
is terribly important to OSR5.  For instance, the "BIOS ID" above tells
you whose motherboard BIOS you have, which sometimes helps trace down
bugs (especially boot bugs).

There is a standard for BIOS ROMs which includes a method of
checksumming them to verify their integrity.  Whatever adapter ROM that
is, its checksum is bad -- the ROM is either a defective unit, or the
vendor did not follow the protocol for proper checksumming.  I don't
know how common it is for BIOS ROMs to ignore the checksumming protocol
(I've never noticed one like that before, but I wasn't looking).

If you run `hw -v -r rom`, it will search each ROM for text strings.
This will help you figure out which device's ROM has the bad checksum.

But it's a red herring.  The BIOS checksum is just an aside, like if my
mechanic told me "yeah, it won't start, and I'm working on that; by the
way, did you notice that the left rear running light is out?".  Not the
cause of the problem.

Go get us some good information about the panic.

>Bela<

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