[mythtv-users] does setpci latency_timer fail on some mobos?

Brian Wood beww at beww.org
Mon Jun 4 10:21:44 UTC 2007


Craig Huff wrote:
> I had seen notes on the list about latency and Mark's question finally got me curious enough to look into it, so I found the wiki page about latency.
> 
> Now I suspect unadjusted latency may be the reason I've been getting IOBOUND errors, seeing buffer overflow messages in /var/log/messages, etc.
> 
> Unfortunately, it seems I'm in the same boat as Mark!
> 
> I have an Asus A8N-SLI Premium mobo with three built-in ATA controllers -- 1 PATA, 2 SATA -- and all three (and another device that escapes me right now) won't change latencies.  They are all stuck at zero (0) !!!
> 
> I did verify that I was doing the commands right by changing the latency on one of my PVR cards (from 64 to 0x64=100) and back.  In the process I learned that the value setpci takes is assumed hex and the value displayed by lspci is decimal ;-).
> 
> Seems that Asus mobos have a common thread.  It is as though they put the PCI parameters for built-in devices in ROM and we're stuck with whatever they chose.  In my case, they appear to be the worst possible values for disk controllers -- at least that is what it seems like to me.
> 
> Sigh... And I switched my whole system to this mobo because of a misunderstanding with the difference between APM and ACPI alarm settings.  I may have to go back to my old one and see if it works better.  A lot of work to do that, but if I can't find another way to handle the load of three simultaneous Hauppauge PVR-x50 recording streams, mythcommflag streams from previous recording(s), and potentially a mythburn job, I may compel myself to build a mythtv system from scratch again (third time!).
> 
> 
> Any advice welcome.

I'm not sure what's going on here with your text not wrapping, not sure
what the "Yahoo Mailer" is doing.

Next: Only on your second build? A Tyro if I ever heard of one :-)

I have a mobo similar to yours, and the latencies report as zero as you
say yours do, and don't seem settable. Note that I say "report as", they
may well actually be something else.

I have no problems with 4 PVR recordings and a commflag job. I try to
not run mythburn jobs when recordings are taking place.

The one difference I see is that I am using a RAID0 array (Linux
software RAID) consisting of 2 SATA drives to store the recordings. I
know it doubles the chance of a drive failure taking out the storage
directory, I'm willing to take that risk.

I'm really not sure if the RAID0 is necessary. I thought it would be
when I built the system over a year ago, and since it's working I have
no reason to change it now.

Whether you want to try that is up to you, obviously. Sounds like  less
work that a mobo changeout, but it depends a bit on your precise drive
configuration. I have an 200GB PATA for the OS and Myth, and a pair of
250GB SATAs for video storage. This box was built before the 500GB
drives became cheap.

BEWW


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