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Date: Wed, 23 Aug 1995 10:37:28 -0500
From: Jim Lowe <james@miller.cs.uwm.edu>
Message-Id: <199508231537.KAA26926@miller.cs.uwm.edu>
To: rgrimes@gndrsh.aac.dev.com
Subject: Re: Matrox Meteor Video Capture Card Driver
Cc: current@freebsd.org, se@ZPR.Uni-Koeln.DE, tinguely@plains.nodak.edu
Sender: current-owner@freebsd.org
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> From: "Rodney W. Grimes" <rgrimes@gndrsh.aac.dev.com>
> 
> The NCR runs it's firmware from the host memory, try cranking the PCI
> latency timer down for the NCR card and see if that helps.  (This is
> in the PCI bios setup screen).  Depending on motherboards (I happen
> to know what ``Triton'' board Jim just tried this in) there maybe
> 1 setting for all slots, or each slot may have it's own setting.
> 
> Either way, crank it down to about 40 (default should be 80).
> 
> From: se@zpr.uni-koeln.de (Stefan Esser)
> 
> Did you try lower values of the "PCI Latency 
> Timer" of the slot the Matrox has been put in ?
> 
> (This timer determines the number of bus clocks
> a PCI card may claim ownerchip of the PCI bus,
> if another card wants to start a transfer.
> The NCR executes its instruction stream from 
> host RAM, and it may get into trouble if it 
> can only get another instruction every 10us ...)
> 
> A latency timer setting of some 0x20 for the 
> matrox should allow the NCR to access the bus
> once per micro second. Guess this is a good
> value ... 
> 
> (The latency timer doesn't force the PCI device 
> to give up bus ownership if there is no request
> from another device and thus doesn't slow down
> the Matrox unless it makes the NCR starve ...)
> 

I tried lowering the PCI latency timer from 80 to 40, then to 20, then 1,
then 0.  It helped me get a few frames at 640x480 before the machine
hung.  I also tried disabling the cpu to pci burst mode.

I have been running the meteor in a machine with and adaptec controller
for 5 days and it never hung.  I am still not sure why the machine
hangs with the ncr controller.

	-Jim