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

[Dylan R. Semler]

<http://www.mythtv.org/wiki/index.php/PCI_Latency>

>> I found my IDE controller latency was set to zero, so I reset it to 
>> 32 (20hex).  I'm not at home to try playback right now, but I was 
>> wondering what others who are having this problem find for their 
>> IDE/SATA controller latency.  Maybe this could fix us up?!?!  I'll 
>> report back later tonight what I find out.
>>
>
> So far, with a very limited number of samples, the people who have 
> found their disk controllers set to zero have either been unable to 
> reset the latency value, or have not seen any positive results from 
> doing so.
>
> Only the machines which have drive controller latency set to 32 or 64 
> initially have had much luck in adjusting them.
>
> Again, this is from a *very* limited number of samples (6 to be exact) 
> so please report your results, positive or negative, as well as the 
> chipset your mobo is using (perhaps on the WiKi page ??)

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