[lug] external monitor question

Davide Del Vento davide.del.vento at gmail.com
Mon Nov 7 21:29:11 MST 2011

Thanks to both, now the monitor is working fine :-)

The details for the curious.

The UseBIOS (in /usr/lib/X11/xorg.conf.d/ this is Ubuntu and has a
very different way to set up xorg.conf) didn't have any effect.

The laptop exhibited the very same problem with a different LCD
monitor and a different cable (another computer worked fine with both
monitors and cables). So, it must have been the laptop. I wasn't
convinced it was a hw problem (not sure why :-) I dug a little more
and found the solution: adding the file /etc/modprobe.d/radeon.conf
with contents "options radeon new_pll=0 modeset=0" (in fact, this is a
radeon X1400 VGA card). Of course this didn't come out of the blue,
but from these bugs
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/541501 (and a few
related/duplicated ones).

Now, the weird thing is that those bugs claim that the fix has been
implemented in kernel v2.6.34-rc4  and closed. I'm running
2.6.32-34-generic, so either the fix has been dropped, or it's a
related thing with the same solution. I will sleep on it and report
tomorrow to the developers, just in case.

Thanks for your suggestions.

On Sun, Nov 6, 2011 at 22:17, Anthony Foiani <tkil at scrye.com> wrote:
> Davide Del Vento <davide.del.vento at gmail.com> writes:
>> The question: do you think this is hopeless and I should give up
>> (given the 60hz vs 50Hz of the power line in Europe vs USA), or do
>> you think that I should eventually be able to find a non "waving"
>> mode?  Ah, I also tried on laptop battery instead of power brick,
>> FWIW.
> Most name-brand computers and peripherals have used "worldwide" power
> supplies for a while now (10-15 years): they can generally take
> anywhere from 90-240V, 50 or 60Hz.  (Exceptions would be devices that
> require large amounts of power, e.g., large laser printers).  So that
> shouldn't be an issue.
> Likewise, VGA is a worldwide standard.  (Europe vs USA use different
> TV standards, but VGA should be fairly universal.)
> Do you have another cable that you can try this with?  I've
> encountered some very low-quality VGA cables, and especially for
> higher resolutions, the "high integrity" or "low signal loss" cables
> are much better.  (They also tend to be quite a bit bulkier, which can
> be a hassle if you intend to use this for connecting to projectors or
> whatnot...)
> Do you have another external monitor that you can try?
> It really sounds like a signal quality issue; whether it's in the
> laptop, the cable, the monitor, the firmware on the monitor or laptop,
> I don't know.
> Good luck,
> t.
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