From owner-freebsd-hackers  Wed Sep 25 13:02:52 1996
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To: "Mike Durian" <durian@plutotech.com>
cc: Stefan Esser <se@ZPR.Uni-Koeln.DE>, Bruce Evans <bde@zeta.org.au>,
        freebsd-hackers@freebsd.org
Subject: Re: Special Cycles on the PCI bus 
In-reply-to: Your message of "Wed, 25 Sep 1996 13:20:36 MDT."
             <199609251920.NAA22022@pluto.plutotech.com> 
From: David Greenman <dg@root.com>
Reply-To: dg@root.com
Date: Wed, 25 Sep 1996 13:01:35 -0700
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>On Wed, 25 Sep 1996 20:06:25 +0200, Stefan Esser <se@zpr.uni-koeln.de> wrote:
>>
>>Well, but those are only used for config space accesses,
>>and config space is normally not touched at all, after 
>>the PCI probe and attach are complete.
>
>  I tracked down those accesses to 0xfca0.  They are completely
>normal.  That is just where the ahc's I/O space got mapped.
>The accesses were caused by the code in aic7xxx.c:ahc_scsi_cmd().

   Hmmm, this is starting to get interesting to me. This also happens to be
the same place where we've seen hangs on P6 machines when doing lots of ahc
disk I/O.

-DG

David Greenman
Core-team/Principal Architect, The FreeBSD Project