[mythtv-users] 2 of 3 HD-5500 cards seen on power up, all 3 on reboot?

[Brian Wood]

On Friday, October 08, 2010 06:25:35 pm Tom Dexter wrote:
> On Fri, Oct 8, 2010 at 8:18 PM, Brian Wood <beww at beww.org> wrote:
> > On Friday, October 08, 2010 06:05:17 pm Tom Dexter wrote:
> >> This one's been driving me insane forever.  My backend has three
> >> HD-5500 cards.  When I power up, without fail, it sees only two of the
> >> three cards.  However it always sees all three on reboot...drives me
> >> nuts.
> >> 
> >> Any idea what could be causing that?  I always figured it was some
> >> sort of anomaly regarding power or something.  I was hoping there
> >> might be some sort of udev configuration that might affect this.
> >> 
> >> At a bare minimum I'd like to at least know if there's a udev command
> >> I could use to find the card without rebooting.
> > 
> > Is this something new? Did it work properly once?
> > 
> > If it worked once:
> > 
> > First thing I'd start looking into is a PSU problem. Those cards draw a
> > fair amount of power (for a non-graphics PCI card). The PSU might be
> > struggling to power them all, and might take a while to do so. The
> > voltage might drop while the drives are spinning up, and be OK after
> > they are all up to speed, and you might have a card that's not happy
> > with the sagged-down voltage. On a reboot, the drives are already
> > spinning, and would not pull the voltage down as much when rebooting.
> > 
> > If you have anything you call pull to reduce the total power draw, see if
> > that makes a difference.
> > 
> > Might also be interesting to run lspci when in the "failed" condition, to
> > see if all 3 cards are seen.
> > 
> > 
> > If it never worked correctly, there might be an issue with process timing
> > at boot up.
> > 
> > This is just speculation, but experience tells me that most "odd"
> > problems are often PSU-related.
> 
> You're probably correct.  I'm pretty sure the issue used to be
> sporadic whereas now it always happens.  A couple of years ago I has
> the PS go and replaced it in a hurry with what I know know is probably
> a pretty cheap power supply.  It's a 400W PSU where the original Dell
> was only 250 I believe, but it is more a less a cheap-o.
> 
> I've been thinking about replacing it with something good.  You're
> also right that I should power up and see if lspci sees it.


Of course Dell probably didn't spec the PSU with three capture cards in mind.

It's always nice to have a known good PSU, though sometimes it can be hard to tell, I've seen "Name" brand units that were 
crappy, and some no-names that were actually well-made.

The PSU is one of the first places a builder will cheap out to save money.

One way to tell is the unit's weight, if a "500-watt" PSU weighs about an ounce I'd start to worry. Good inductors and 
transformers have a fair bit of heft, of course good electrolytics and bad ones weigh about the same :-)

PC Power and Cooling, and Thermaltake, sell OK units, as does Antec, IMHO.

Take a good look at the capacitors on the mobo as well, that's a common source of problems.