Two display anomalies

[Matthew Saltzman]

On Tue, 13 Sep 2005, Tim wrote:

> On Tue, 2005-09-06 at 20:58 -0400, Matthew Saltzman wrote:
>> (1)
>> Video card: NVIDIA GeForce 2 MX (generic)
>> Monitor: Samsung SyncMaster 930B (flat panel)
>> Driver: nvidia (the commercial one), but it happens as well with nv.
>> Resolution: 1280x1024, 32-bit color or 16-bit color
>> Sypmtom: Monitor flickers as if it's synching at very low rate.
>> The monitor reports that it is syching at 75Hz, but I still see flicker.
>
> Display refresh rate beating with the room lighting?

No, it happens when room lights are off too.  This one turned out to be 
the video card not being able to sync reliably at 75Hz.  A newer video 
card did not exhibit the problem.  Workaround: cap vert refresh at 60 Hz.

>
>> (2)
>> Video card: ATI Radeon Mobility 7500 in an IBM Thinkpad T41.
>> Driver: radeon
>> Kernel: kernel-2.6.12-1.1398_FC4
>> Kernel option: video=radeonfb
>> X: xorg-x11-6.8.2-37.FC4.45
>> Symptom: When I use the VGA-out jack to connect to an overhead projector
>> or external monitor, the projector image ripples slowly, as though (very
>> narrow) waves are passing over it.
>
> Sagging mains power in the projector?  Earth loops?  Monitors placed
> near to another device emitting a strong EM field?

Nope.  Same machine works fine in Windows on the same projector.  Same 
behavior on multiple projectors.  Projectors mounted in the ceiling, away 
from other devices.  Also happens on standalone monitors in various 
locations.

When I can reach the reset button on projectors or flat panel monitors, 
resetting seems to clear the problem.

-- 
 		Matthew Saltzman

Clemson University Math Sciences
mjs AT clemson DOT edu
http://www.math.clemson.edu/~mjs