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Date:      Fri, 22 Mar 2002 00:15:29 -0800
From:      Terry Lambert <tlambert2@mindspring.com>
To:        ?? <pcdvd.master@msa.hinet.net>
Cc:        freebsd-smp@FreeBSD.ORG
Subject:   Re: SMP Error in VIA 694 based bord
Message-ID:  <3C9AE821.6A4B47ED@mindspring.com>
References:  <CKEELIENECBJLIHMDDBIEEACEAAA.clients@dreamtime.net> <3C992BE9.169C1501@mindspring.com> <00b101c1d16c$ea162ec0$eb1148d3@chris>

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?? wrote:
> 
> thanks to Terry, I added option DISABLE_PSE,then the smp works fine,I
> already boot over 30hrs,and running stable, thank
> you for your help.
> May I ask you? what is PSE,it seens like a cpu function?

Thanks for posting to the list.  People generally don't
believe the FreeBSD has a PSE problem, without a confirming
success report in the DISABLE_PSE case, like yours.  Actually,
Satoshi Asami and the people still at ClickArray should be
able to conrim the problem as well as the workaround.


It is the page size extension for the use of 4M pages.

There is a subtle bug in both Intel and AMD processors with
regard to the PSE.

FreeBSD used to accidently work around it.  Apparently, it
no longer does.

By disabling the PSE, you prevent the use of 4M pages, which
avoids triggering the bug in the first place.

If someone who cares about 4M pages wants to narrow down the
code change that resulted in FreeBSD no longer working around
the problem, it night be useful to seperate the use of the PSE
for the kernel from the use of the PSE for memory mapped
devices.

-- Terry

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