Date: Wed, 23 Aug 1995 10:37:28 -0500 From: Jim Lowe <james@miller.cs.uwm.edu> To: rgrimes@gndrsh.aac.dev.com Cc: current@freebsd.org, se@ZPR.Uni-Koeln.DE, tinguely@plains.nodak.edu Subject: Re: Matrox Meteor Video Capture Card Driver Message-ID: <199508231537.KAA26926@miller.cs.uwm.edu>
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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
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