[ltp] dual head Failing video or bad Xorg settings?

[John Locke]

Hi,

I've been using my T41 with Mandrake 10.1, with no major issues for the 
past year. A couple weeks ago I installed Mandriva 2006 to get some of 
the new features--wireless management, suspend, hibernate, etc. Most of 
those are working fine. However, I'm starting to have trouble with my 
dual head configuration.

When I connect my external LCD monitor through the VGA connection and 
start X, I get some weird flashing/streaking horizontal lines on the 
laptop screen. The framebuffer and console are absolutely fine (with 
nothing appearing on the external display). The laptop with no external 
monitor connected/MergedFB off, works fine, too. It's only when MergedFB 
is on, at certain resolutions, that this is a problem. And, what's 
worse, it worked fine in the past, with the same xorg.conf file.

I first noticed it after using Xrandr to switch from a MergedFB 
xinerama-faked mode to a cloned mode, and disconnecting the external 
display. I've been doing this to quickly disconnect the external 
display, before taking the laptop somewhere. This used to work fine, 
even since upgrading the OS--but now the flashing streaks appear. Have I 
fried something in the video card by connecting/disconnecting the 
external display while X is running?

I've found that if I cycle through the screen resolutions, certain 
combinations work fine, but most do not. Right now, a combination of 
1400x1050-800x600 in clone mode works--the other resolutions came up 
with streaks. But after shutting down the computer, starting up again, 
and cycling through a couple of resolutions I eventually got my main 
setting (1400x1050 on the internal, 1024x768 on the external, its native 
resolution) to work with only minimal streaking on the internal monitor, 
which went away after moving some windows around.

Once it goes away, it seems to stay stable for a while. I'm wondering if 
it has to do with RAM used for video?

Any ideas for troubleshooting this, or is it going to continue to 
deteriorate on me? Anybody else experience this?

Xorg details:
xorg-x11-6.9.1.cvs20050915 (default for Mandriva 2006)
radeon driver
Section "Device"
    Identifier "device1"
    Driver "radeon"
    Option "DPMS"
    # acceleration
    Option "AGPMode" "4"
    Option "AGPFastWrite" "on"
    Option "RenderAccel" "on"
    Option "DynamicClocks" "on"

    # Enable power saving--disable if hangs
    Option "EnablePageFlip" "on"

    # Dual display - external is native 1024x768 LCD, connected through VGA
    #Option "MergedFB" "on" - off to allow single head if no monitor 
connected
    Option "MergedNonRectangular" "On"
    Option "CRT2Position" "LeftOf"

    Option "MetaModes" "1400x1050-1024x768 1400x1050+1024x768 
1400x1050+800x600 1400x1050 1024x768 800x600"
    Option "CRT2VRefresh" "60"
    Option "CRT2HSync" "31-90"
EndSection

Cheers,

-- 
John Locke
"Open Source Solutions for Small Business Problems"
published by Charles River Media, June 2004
http://www.freelock.com