[mythtv-users] 0.19, XvMC, and Prebuffer pause

Todd Ignasiak ignasiak at gmail.com
Wed Mar 1 21:58:15 UTC 2006

On 3/1/06, Dawning Sky <the.dawning.sky at gmail.com> wrote:
> On 3/1/06, Dylan R. Semler <dsemler at macalester.edu> wrote:
> > <http://www.mythtv.org/wiki/index.php/PCI_Latency>
> I just tried changing the latency on my three machines.  I have two Dell
> 8200 desktops from about 2002 and a Sager laptop from December 2005.  In
> all three machines, the initial IDE latency was 0 and changing it with
> setpci -v -s 00:1f.1 latency_timer=b0 (or any other value)
> did not seem to do anything.  At least lspci -v continued to display
> their latency as 0 (I have not been able to test this with Myth yet).
> Furthermore, I found that if tried this command on ANY controller whose
> intial latency was 0, the command did nothing.  If the initial latency
> was not zero, the command would change the latency to the desired
> value.  I Also tested that if a controller ititially had a non-zero
> latency, and I changed it to zero, I was still able to change it back to
> other values.  I have no idea why this is or what can be done, but I
> thought I'd add some more datapoints to the set.  If anyone wants the
> maker of these mobos, I can probably find that out somehow.
> Dylan
> Ditto here.  Dell Dimension 8250 P4 2.4GHz Intel 828 chipset.

I used setpci to adjust latencies on my Asus K8V motherboard (athlon 64
3200+), and it wored fine.

One question I have is:  Does the AGP latency setting effect the PCI bus at
all?   My AGP card's latency was set to 254 (max).    I am assuming that the
AGP bus is completely separate, so I don't need to tweak that setting.  Can
anyone confirm/deny this?

Also, there is the issue of shared interrupts, which I have seen cause big
problems doing HD video in the past.   Theoretically, my system (using APIC)
should have plenty of interrupts available,  enough to give each device its
own.    But, for whatever reason, all the active devices are clustered
around a few interrupts..  My AGP video card, and two tuners share a single
interrupt.   Three other tuner devices are on another one.   Those two
interrupts have a huge percentage of the overall system interrupts.

Is there any way to force Linux to distribute the IRQ's differently?
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