Re: [gentoo-amd64] Re: kernel.org vs. Gentoo-64 bit kernels (xruns)

[Mark Knecht]

On 9/20/05, Paul de Vrieze <pauldv@g.o> wrote:
> On Tuesday 20 September 2005 14:25, Mark Knecht wrote:
> > On 9/20/05, Duncan <1i5t5.duncan@×××.net> wrote:
> > > I'm not familiar with the term "xrun", so this may be entirely off the
> > > wall, but have you confirmed the hard drive is running DMA?  If your
> > > chipset or SATA drivers are wrong, and your hard drive is having to run
> > > in legacy interrupt mode instead of DMA mode, it *WILL* destroy latency
> > > and generally make the system unusable for any sort of real-time work at
> > > all, regardless of the other kernel patches applied.  So... in addition
> > > to checking the network drivers, investigate the hard drive and chipset
> > > I/O drivers as well, and confirm you ARE running DMA mode.
> >
> > Thanks, yes, DMA is running, as far as I can tell. hdparm -tT returns
> > numbers that are >50MB/S.
> >
> > xruns are a term specific to the Jack server
> > (jack-audio-connection-kit) that tell us whether we've had and overrun
> > or an underrun. It's would be off topic to go deeply into how Jack
> > operates when talking to sound cards, but take it to mean something
> > bad has happened with real-time audio data.
>
> Nah, it's more alsa specific. What soundcard do you use? Some soundcards are
> more crappy than others (especially onboard ones). I guess it should support
> DMA as even the soundblaster pro did so. Soundcards do however provide
> various levels of hardware accelleration.

That's not the problem here. The card is an RME HDSP 9652. It ran in
my older Asus/Via/Athlon-XP/Gentoo-32-bit machine just fine. I've
built the new Asus/NForce4/Athlon64/Gentoo-64-bit machine and
transfered the same card of here so I know the card and drivers are
fine, at least in a 32-bit environment.
>
> > Interestingly Jack runs from memory so hard drive performance should
> > not cause major problems unless it's not interruptable in a more or
> > less real-time way. On my Gentoo 32-bit machines (using Via and ATI
> > chipsets) I've not had to install any real-time patches and can still
> > run reliable at sub-2mS latencies. On those machines I can do pretty
> > much anything, browse the web with firefox, do and emerge sync, etc.,
> > and I get no xruns. On this AMD64/NForce4 machine and emerge sync
> > causes xruns immediately, indicating the sound card is getting starved
> > for data.
>
> Good chance the soundcard buffer is smaller or the driver is crappy. You could
> try to take the soundcard from the old machine and put it in the new one.

As you can see, that's what I did! :-)

- Mark

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