[mythtv-users] problems on playback due to no ACPI and IRQ sharing?

[Andrew Gallatin]

Norman Lyon [yourdog at poboxes.com] wrote:
> I'm thinking that the problems I'm having with my playback skipping a little
> (maybe a quarter of a second) every few minutes may have something to do with
> lack of ACPI/how my IRQs are used.  It looks like EVERYTHING except the onboard
> IDE shares IRQs, 3, 5, & 11.  That looks to be causing a lot of conflicts
> between my audio cards, capture card, video card, and extra IDE card.
> 
> Can anyone verify whether or not they've either been able to track down problems
> to this, or at least had a high level of suspicion that this may have caused
<...>

You may want to try shuffling your PCI cards around to try to find
a better sharing of IRQs.  That really helped me on a system
with ACPI and hyperthreading, running an SMP kernel.

I think it sometimes matters much more *which* devices are sharing
IRQs, than the fact that the IRQs are shared.  Eg, if you have 2
devices which both are well behaved, its not really that bad to have
them share an interrupt.  But if you have a driver for "slow" hardware
(where it needs to read/write registers with lots of delays just to
see if the card sent an interrupt), or a buggy driver, it can
adversely affect the other driver that it is sharing an interrupt
with.

For example,  I have a PCI wireless card where I'm using a Windows
driver via ndiswrapper.  Every 5 seconds, that driver does *something*
which resets the card.  Until I moved it to a slot where it got its
own irq, it would hang the system for a few hundred milliseconds every
5 seconds.  Now that it has its own IRQ, it just hangs the wireless
connection.    Needless to say,  I'm getting rid of this card..

Drew