Two display anomalies

[Jeff Vian]

On Tue, 2005-09-06 at 23:01 -0400, Matthew Saltzman wrote:
> 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?
> 

You need to manually edit /etc/X11/xorg.conf to change those settings.
With my flatpanel monitor (samsung syncmaster 213T) I had to manually
change the VertRefresh from the range of 56.0 - 75.0 which was set by 
system-config-display   to a range of 60.0 - 60.0 in order to get the
monitor to allow the maximum resolution of 1600x1200.  Did not have to
change the HorizSync settings at all.

> >
> > 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
>