[LAU] IRQ and RT question

Len Ovens len at ovenwerks.net
Thu Dec 6 22:18:44 UTC 2012


On Thu, December 6, 2012 8:49 am, Aaron Krister Johnson wrote:

> Anyway, it seems the EEE has suboptimal IRQ hardware settings for RT low
> latency audio...doing less /proc/interrupts shows that there's a lot of
> sharing, like the audio and video card being on the same IRQ. Indeed,
> running Csound FLTK gui interfaces and moving them while processing the
> csound orchestra sometimes makes pops and crackle dropouts, while the same
> thing on the better IRQ set HP Pavilion shows flawless performance.
>
> Even if I run an outboard USB audio interface (Lexicon Lambda) on the EEE,
> there is still suboptimal USB Irq settings to contend with.

It is unusual that the internal Audio IF is sharing an irq, even my cheap
netbook has the internal audio IF on it's own irq and it is the highest
one at that (irq 48... some OS work better that way) I have found that
even though my wireless is not on the same IRQ, it still interferes with
my audio and gives xruns (pops) about once a minute... worse when
disabled, unless I unload the kernel module for it. You may wish to try
unloading other modules (like the built in camera for example is another I
have heard can interfere). It is also possible to disable some USB ports
to clear an IRQ if needed. I found that just using a different USB plug
helped too. The port on the right side of the netbook gives better results
than the one on the left.... The one on the left shares IRQs, the one on
the right does not.
I checked which USB port hey were by looking at the last 10 or so lines of
demsg while plugging a USB memstick in different ports. It shows which USB
port you have just used. Mine go from USB1 to USB5, USB3 is a good one for
me, but your's may be different.


-- 
Len Ovens
www.OvenWerks.net



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