linux-kernel - Re: kernel won't boot on a Cyrix MediaGXm (Geode )

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Message-ID: <4886DA32.6080401@sieb.net>
Date:	Wed, 23 Jul 2008 00:13:54 -0700
From:	Samuel Sieb <samuel@...b.net>
To:	Juergen Beisert <jbe@...gutronix.de>
CC:	linux-kernel@...r.kernel.org
Subject: Re: kernel won't boot on a Cyrix MediaGXm (Geode )

Juergen Beisert wrote:
> On Dienstag, 22. Juli 2008, Samuel Sieb wrote:
>> Juergen Beisert wrote:
>>> linux-2.6.25/arch/x86/kernel/cyrix.c, line 151. Disable this line or
>>> change the value 0x04 according to the speed of your CPU. This tweak
>>> helps others with random hangs of their system.
>> I tried various values and various combinations of commenting out lines
>> and the only one that worked for me was to comment out the PCR1 line
>> just above it.  With that line commented out (or both of them), it
>> boots.
> 
> Hmm, then your BIOS does know more about your hardware than the kernel. ;-)
> The PCR1 line enables the incrementor. If disabled the value in PCR0 doesn't 
> matter.
> 
I did some more testing and the end result is that you can't enable the 
incrementor on this cpu.  I tried values from 0 to 7 for the PCR0 and it 
always crashed or hung (0 also gave noise all over the screen).  The 
values set by the BIOS are PCR1: 1 and PCR0: 0.
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