[lug] Laptop screen snow affected by software?

[Zan Lynx]

On 4/14/10 11:38 AM, Chris Riddoch wrote:
> My laptop (an old and gradually dying T4 Thinkpad) started doing
> something interesting late last week - I'm getting snow on the screen,
> after X has been running 10-20 seconds.  Of course, my natural
> assumption is a failing connection between the screen and the rest of
> the system.
>
> Here's the weird thing: when I plug the laptop into an external
> monitor, X goes into what appears to be a lower resolution, puts the
> display up on both external and built-in screens... and the snow
> completely disappears from the laptop display!  Evidently, there's
> something software-related about this snow, which strikes me as odd,
> given the likelihood that it's really just a bad cable.  Back in the
> days of CRTs, snow would come and go at different resolutions until
> the proper X settings were arrived at - it makes sense, after all, the
> connection between the two was rather analog.  But on a laptop screen,
> where the display hardware has a lot more control over the pixels,
> snow suggests connection problems to me.
>
> So my question: Just how can snow on a laptop screen be affected by
> *software*?  Any suggestions, besides the obvious "buy a new laptop"
> (which I'll do as soon as finances allow, of course.)  Looks like I
> won't be at 1400x1250 again anytime soon.
>

You said that it goes to a lower resolution?

Have you tried running the laptop display at a lower resolution without 
the external monitor?

It may be that the components have developed a flaw that makes them fail 
at higher frequencies but work just fine at the slower speeds. Lower 
resolutions require less work from the hardware.

It could be a flaw in the graphics processing chip or in the LCD driver. 
If it displays fine on the internal screen in lower resolution I doubt 
its a cable problem.

-- 
Zan Lynx
zlynx at acm.org

"Knowledge is Power.  Power Corrupts.  Study Hard.  Be Evil."