Two display anomalies

[Matthew Saltzman]

On Tue, 6 Sep 2005, Bob Chiodini 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.
>>
>> (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.
>>
>> In FC3, this behavior varied with the kernel version.  In FC4, I need this
>> kernel in order to get proper ACPI behavior, so I haven't tested much.  In
>> WinXP, the display is rock-solid.
>>
>> For (1), could this be the monitor?  It's brand new.  I also recently
>> installed a TV tuner card, but that doesn't seem to be too likely a
>> culprit.  I didn't *think* I was seeing the flicker before that, but it's
>> my wife's monitor, so I didn't spend much time with it.  My machine (CRT,
>> no TV tuner) is rock solid.
>>
>> If it's not the monitor, what should I be looking for to further isolate
>> the problem?
>>
>> For (2), I'm pretty convinced it's a bug, but I' not sure what component
>> to report it against.  In FC3, it varied with kernel version, with
>> whatever XFree/xorg was installed.  So I'm sort-of thinking kernel.
>>
>> Thanks for any suggestions.
>>
>> --
>>  		Matthew Saltzman
>>
>> Clemson University Math Sciences
>> mjs AT clemson DOT edu
>> http://www.math.clemson.edu/~mjs
>>
>
> Matthew,
>
> 1) Try lowering the vertical refresh to 60 Hz.  I'm not familiar with
> that display, but both the Dell and the Viewsonic recommend 60 Hz.

Is this an xorg setting?  The refresh rates are what is selected when I 
run system-config-display.  There doesn't seem to be a way to set this in 
the monitor menu.  How would I set it?

>
> 2) Are the vertical and horizontal rates the same between Windows and
> FC4?
>
> Are they the same laptop?
>
> If you answered yes to both then I'm stumped.

Yes, it's the same laptop running WinXP and FC4 and FC3 with several 
different kernels.

>
> But...
>
> If the refresh rates are not same then adjust FC4 to the same as
> Windows.
>
> The problem sounds like a bad/low quality cable. Cable performance will
> get worse as the refresh rates go up.  Could also be a grounding problem
> inducing hum in the video signal.
>
> If Windows and FC4 are not running on the same laptop then I would
> suspect a hardware problem with the FC4 laptop.

That's two suggestions for the cable.  I will try some others, but it's 
not clear why the same projector and same cable and same hardware behaves 
differently when I use different software.

Thanks for the suggestions.

>
> Bob...
>
>
>

-- 
 		Matthew Saltzman

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