Re: [linux-audio-dev] Re: [announce] [patch] Voluntary Kernel Preemption Patch

Andrew McGregor
2004-07-22T22:25:43Z

--On Wednesday, 21 July 2004 12:53 p.m. +0200 Florian Schmidt
<mista.tapas@gmx.net> wrote:

> Hi,
>
> interesting that you mention the Xserver. I use a dual graphics card
> setup atm [Nvidia GF3 TI and some matrox pci card]. The nvidia card seems
> to work flawlessly even with HW accelleration [i use nvidias evil binary
> only drivers]. The matrox card OTH disturbs the soundcard severely.
> Whenever i have activity on my second monitor i get sound artefacts in
> jack's output [no cracklling, it's rather as if the volume is set to 0
> for short moments and then back to normal]. There's a certain chance that
> this artefact produces an xrun. I suppose it's because the card is on the
> pci bus.

<snip>

> Should i try a different 2nd gfx card? Should i avoid pci gfx cards at
> all costs? Will i just have to live w/o second monitor? How do i find
> out which hw resources X is really using?
>
> Florian Schmidt

It is a PCI bus issue. You simply don't have enough PCI bus cycles
available to do what you want to do. The resource you're running out of is
bus bandwidth, and there's nothing to be done about it, other than remove
the PCI gfx card from the system.

If you get another dualhead AGP graphics card (anything will do), the
problem should go away. We have a developer who does lowlatency
multichannel sound stuff on a machine with a Matrox G450 dualhead card no
problem. I expect my own system (Radeon 9800 Pro and M-Audio 1010LT audio)
would be fine dualhead too, although I only run it singlehead at the
moment. The 1010LT is 10 channels in and out of 24-bit 96kHz audio and
works great down to 1.5ms buffers, so it is no small bus load itself.

Andrew

---------
Andrew McGregor
Director, Scientific Advisor
IndraNet Technologies Ltd
http://www.indranet-technologies.com/

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