[LAU] real time audio and graphic/ interrupt tweaks?

david gnome at hawaii.rr.com
Tue Jul 28 05:09:35 EDT 2009

Unless there's an option to change interrupts in the netbook's BIOS, I 
don't think there is. In most laptops, those kinds of interrupts are 

I find usbview more useful for figuring out USB hierarchies, but maybe 
it's just me being more visual. KInfoCenter is informative, too.

On my Toshiba, USBView shows that I have one EHCI host controller (USB2) 
with a USB 2.0 hub (internal) hub that currently has 2 USB2 devices 
attached to it - another USB 2.0 hub (external) and an external hard 
drive (attached to a physical port on the laptop, not on the external hub).

It also shows that I have a UHCI host controller (USB 1.1) that 
currently has my USB sound card attached to it.

That takes care of all three physical ports on this laptop.

KDEInfoCenter irqs report a UHCI controller with 3 busses using IRQs 16, 
18 and 19; and a EHCI controller using IRQ 23.

So it looks like the USB2 controller is using 3 IRQs and the USB 1.1 is 
using only one. So it looks like one IRQ per bus.

I'm just figuring this stuff out myself, so perhaps someone who really 
knows stuff about USB can really explain what's going on?

Martin Horn wrote:
> Hi again,
> thanks for your answers!!
> As the computer is a netbook it has only 2 usb ports both on bus 2 and 
> this shares the interrupt with the graphics (intel controller), is there 
> a way to alter these interrupt settings? What are the other 3 busses 
> "lsusb" gives me if I have only 2 physical ports both on bus 2?
> Thanks again!
> Martin
> On Mon, Jul 27, 2009 at 9:48 AM, david <gnome at hawaii.rr.com 
> <mailto:gnome at hawaii.rr.com>> wrote:
>     Arnold Krille wrote:
>      > On Monday 27 July 2009 01:36:57 Martin Horn wrote:
>      >> I try to run xwax on ubuntustudio 8.10 on a Panasonic CF-T2
>     subnotebook
>      >> (1Ghz/512MB). Everytime I start real time audio apps like jack
>     the graphic
>      >> gets very slow and freezes for some seconds, also the audio
>     playback is
>      >> like timestretched and sounds filtered.
>      >> I guess it has something to do with interrupts shared by graphic
>     and sound
>      >> (sound comes from a Maya44 USB sound card).
>      >> Can anybody give me a hint how to check or alter interrupt
>     settings or do
>      >> you have any other ideas...?!
>      >
>      > Most computers have more then one usb port. And these usb ports
>     sit on
>      > different irq's, I doubt it that all of them are shared with the
>     graphics.
>     Well, if the OP has an Intel chipset - practically everything could be
>     sharing an interrupt with the graphics. ;-)
>     More important to know which internal HUB the laptop's USB ports are
>     hooked to. My Toshiba laptop has 3 USB ports but only 2 USB internal
>     hubs ...
>      > How do you know which usb port uses which irq?
>      > Check the output of "lsusb" and "cat /proc/interrupts" to see
>     where you audio-
>      > device is connected and which irq that port has.
>     I had similar-sounding problems with my UCA202 USB sound card when I was
>     running it as USB device #7 on a powered external 7-port USB2 hub.
>     Problem went away when I hooked it directly to a port on the laptop.
>     --
>     David
>     gnome at hawaii.rr.com <mailto:gnome at hawaii.rr.com>
>     authenticity, honesty, community
>     _______________________________________________
>     Linux-audio-user mailing list
>     Linux-audio-user at lists.linuxaudio.org
>     <mailto:Linux-audio-user at lists.linuxaudio.org>
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gnome at hawaii.rr.com
authenticity, honesty, community

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