Monitor Reports 1600x1200 vs XRandR Reports 1024x768 - Debian Squeeze

[DanHeli]

Hello,

I am running a Debian Linux machine and am having trouble getting a digital resolution of 1024x768 (desired resolution) out of my mini Display Port->DVI-D adapter plugged into a monitor with a native resolution of 1920x1200.

The problem is that the graphics card makes the resolution look as if it's 1024x768@60Hz, confirmed by running xrandr, but the monitor receives it as 1600x1200@60Hz. If I plug the output into a monitor with a native resolution of 1024x768 the graphics card will output the correct resolution to the monitor, but if the native resolution is greater than 1600x1200 I get the problem result I stated earlier.

I have edited my xorg.conf for the display to accept only the 1024x768 resolution, but I believe this is creating a simulated (or virtual) resolution of 1024x768 and not an actual output resolution.

Section "Screen"
    Identifier "Screen0"
    Device     "Device0"
    Monitor    "Monitor0"
    DefaultDepth   24
    SubSection   "Display"
        Modes    "1024x768"
        Depth    24
    EndSubSection
EndSection

I have tried adding a specific Modeline to my monitor definition, but that proved futile.

Modeline "1024x768" 65.00 1024 1048 1184 1344 768 771 777 806

Anyone know how to get an AMD card on Linux to send a monitor the correct resolution under these conditions?

Thanks for the help,
Daniel

OS: Debian Squeeze x32
Graphics Card: AMD FirePro W600
Driver: fglrx

 

[smeezekitty]

I am curious why you would run 1024x768 on 1920x1080 display.
In any case, how do you know that the monitor is correct on the resolution? What does this page show? http://www.javascriptkit.com/howto/newtech3.shtml

Although 1024x768 vs 1600x1200 should be a very noticeable difference.

 

[DanHeli]

I am curious why you would run 1024x768 on 1920x1080 display.
In any case, how do you know that the monitor is correct on the resolution? What does this page show? http://www.javascriptkit.com/howto/newtech3.shtml

Although 1024x768 vs 1600x1200 should be a very noticeable difference.

The reason I need the lower resolution is because I am outputting the 1024x768 resolution to an overlay device as the foreground. The native resolution of the overlay device's foreground input is 1600x1200, but it accepts a 1024x768 resolution when it is given. I have only been able to accomplish giving this resolution when I first hook up a native 1024x768 resolution display and then hook that same DVI cable to the overlay device without removing the adapter from the back of the graphics card.

I suspect the issue has something to do with X auto-discovering the native resolution of the display it's hooked up to. The graphics card is sending a signal of 1600x1200 (because that's the native resolution of the overlay device), but the resolution is 1024x768 (so the 1024x768 image is stretched over a 1600x1200 actual resolution).

Just to be clear, I am not only testing this configuration on a black box overlay device, I am also using ASUS monitors whose native resolution is 1920x1200. Whenever I am hooked up to the ASUS monitors, I get the same issue (only the resolution is 1920x1200 instead of 1600x1200).

Running...

xrandr --verbose

I can see that the resolution is in fact 1024x768, but it is set to fit a 1600x1200 display.

Result:

  1024x768 (0x206)  162.0MHz +HSync +VSync
        h: width  1024 start 1664 end 1856 total 2160 skew    0 clock   75.0KHz
        v: height  768 start 1201 end 1204 total 1250           clock   60.0Hz

As you can see, the "start" and "end" for the horizontal and vertical is ~1600 and ~1200.

I have tried creating a new mode using "gtf" commands in conjunction with "xrandr --newmode/--addmode", but those resulted in X reverting back to the previous setting.

I have not tried going to the website you've suggested, but I expect the results to be similar to what xrandr is presenting. I will visit the site next I get to the machine and post the results shortly after.

Thanks again.

 

[smeezekitty]

If xrandr is showing 1024x768, chances are that is the actual resolution.
Virtually all monitors will scale up to fit the entire screen.

Then again I might be confused. X11 is generally a huge pain in the butt.