[mythtv-users] Stability problems with 9400GT and VDPAU

Tyler T tylernt at gmail.com
Wed Jul 14 21:10:07 UTC 2010

> I've been getting some random lockups that end with corruption of the
> video and I'm trying to figure out what to do about it.
> What I didn't know before purchasing was that this particular card
> claims to need at least a 300 watt PS. Is that normal of these types
> of cards?

I'm afraid they are rather power hungry. I had to upgrade my 60w PS to
80w just to add a little PCI 8400 GS card. That thing is specced at
71w TDP which is probably way more than the PCI bus is designed to
handle! Fortunately, it only seems to need that much juice with heavy
3D action. I haven't been able to test mine yet to know if my 80w PS
will handle my 32w CPU + VDPAU, but I'm keeping my fingers crossed
(and plan to underclock).

> I'm thinking it could either be heat

You should be able to run the nvidia-settings utility to view GPU
temperature. Make Myth non-fullscreen so you can watch the temp as a
recording plays, to verify.

> or lack of power that's
> causing my problems, but power is something I have a limited supply
> of.

Look up the TDP of your particular video card (they vary). (I realize
TDP does not equal current draw, but it's prolly close enough.) Add to
that not only your CPU wattage, but also your hard drive, DVD drive,
etc as well as some fudge factor for DC-DC/VRM losses, fans, etc. Or,
go buy a Kill-A-Watt or similar ammeter and see what happens (remember
a 275w PS at full load will draw probably over 300w at the wall due to
power factor and other inefficiencies).

> The case has a non-standard PS that can't be upgraded easliy so of
> course I'm hoping it's not power.

This is part of the reason I chose a case with an external brick-style
PS. I realize that doesn't help you in the slightest, especially since
it's hard to find bricks rated for more than 120W or so, but I mention
it for the benefit of others to consider uATX or other standardized
solutions over proprietary. Say, one thought does occur to me -- maybe
a PS designed for a 1U rackmount server would fit in your case. It's a
long shot, though.

> If I underclock the GPU, how low can I go before I can't use VDPAU to
> play HDPVR recordings?

We're discussing this a little bit in the nearby "Nvidia underclocking
vdpau" thread. Apparently, nobody seems to know yet, so please try and
let us know what you find. :)

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