HOWTO: change resolution/refresh rate in Xorg

[bmaehr]

Hello!

I was searching for a solution a long time, perhaps someone has an idea.

I have an CoreDuo MiniMac with debian on it. It is connected with a DVI to HDMI cable to a 37" Xoro screen with a resolution of 1920x1080. The screen supports 1080i and 1080p. The video-card is an intel i945gm.

I was able to select a setting of 1920x1080 with 12 Hz at MacOS and thaht works (the mouse pointer is slow but who cares). If I try higher frequencys the screen doesn't recognice the signal. Also 1080i with 60Hz seems to work.

Now i would like to setup linux with xorg to use these settings. I was able to enable 1920x1080 with 915resolution. But if I start xorg it ignores my modeline with 12Hz and chooses 70Hz which is not supported by my TV.
If I try to lower the HorizSync and VertRefresh settings xorg doesn't start with the message "no screens found".

Anybody an idea?

[Domie]

Nice guide, but it didn't work. I'm still stuck on 60Hz...

[Domie]

Well, I finally found it out myself.

https://help.ubuntu.com/community/OpenChrome

Vesa is just not a good driver for me. So I used OpenChrome. How I found out? Thanks to deleting Ubuntu, installing Mandriva which uses the right driver... Now it was just googling...

So I wished I could say thanks to someone, but I can't...

[kaka0502]

I had this scrolling effect. I was successful troubleshooting it by changing driver from vesa to nv. Thanks for the HOWTO.

[vsandz]

thanks mate. worked perfectly and i'm up to 1280x1024 now.

I have one small doubt however. I know this might seem lame but my monitor's user reference states that i can run it @60kHz if in digital mode or @75kHz in Analog mode. I've got both connectors and was wondering if anyone could help me with this digital v/s analog thingy cos i've googled it and cant find enuff info out there. cheerio.

[RedSquirrel]

Adding custom modeline
If you know what your monitor can do, for example 1024x768@75Hz, you can use this page to generate a custom Modeline for you xorg.conf:

• online modeline generator

Copy paste the new Modeline to Monitor section (for example):

 
# 1024x768 @ 75.00 Hz (GTF) hsync: 60.15 kHz; pclk: 81.80 MHz
Modeline "1024x768_75.00"  81.80  1024 1080 1192 1360  768 769 772 802  -HSync +Vsync

Watch that the hsync is in range with the HorizSync on the same section (in this example the range is 31-101 and this modelines hsync is 60.15, so we're safe). Also the VertRefresh and the refresh rate you selected (75Hz in this example) should match - in this example VertRefresh is 60-160 and modeline is 75Hz, so that's all good.

Now you can select the default resolution and colordepth by tweaking the Screen section. It should look something like this:

Section "Screen"
    Identifier    "Default Screen"
    Device        "NVIDIA Corporation NV34 [GeForce FX 5200]"
    Monitor        "CM752ET"
    DefaultDepth    16
    SubSection "Display":
        Depth        16
        Modes      "1024x768_75.00" "1024x768"
    EndSubSection
EndSection

Monitor name here (CM752ET) matches the Identifier on your Monitor Section. Device line here matches the identifier on your Device section - you get the idea? It ties together some settings for your screen - the graphics card and your monitor. You may have more Subsections here, but only one is needed.

Change the DefaultDepth to what you would want it to be, 16 (65536 colors) or 24 (16M colors). Change the Modes line to match the resolutions you want to use - Depth must match DefaultDepth (here it's 16).

Great guide.

I would suggest that you make sure the Modeline and the Modes line match (as I indicated above) in your example just to make it clear that that has to be the case in order for the Modeline to be used. If they don't match, then it won't work.

[heimo]

Thanks! Done. I've been quite active on these forums, trying to help with various resolution/refresh rate problems and this guide has helped myself a lot - no need to remember all the links, cryptic settings etc.

Back in... I think it was 1996, I was trying to get my X working and ESR's howto was really helpful. First it was really confusing, but I soon fell in love with the kind of minute control you actually get of your hardware with GNU/Linux+X.
http://tldp.org/HOWTO/XFree86-Video-...WTO/index.html
(historic howto, not maintained, useful for learning, not for configuring Xorg)

I think it was ESR's, but it must have been older version by Chin Fang.
http://tldp.org/HOWTO/XFree86-Video-...O/credits.html

[agnul]

Not sure if this is related at all but...

I have a DELL dimension 3100 (intel integrated graphics board, i910 i think) and a DELL 1905fp 19" LCD.

X believes the optimal resolution is 1280x1024@75Hz (both in my previous 6.06 and in the freshly installed 7.04), while the monitor reports the optimal resolution as 1280x1024@60Hz. The image is OK, but the most annoying thing is that each time i boot into linux i must fiddle with the monitor controls to re-center the image. I have the same problem (off-center image) when running in text mode.

Any suggestion for fixing this?
TIA.

[zedfrugnug]

I tried adding a modeline, to get the right refresh rate, as suggested, but now my screen looks even worse
System>settings>screen resolution still tells me I'm still at 55Hz, should be 60Hz..
Using nvidia FX5200 with nividia driver and 1680x1050 resolution.
I've set the horizontal and vertical frequency using "sudo dpkg-reconfigure xsever-xorg"

Section "Monitor"
Identifier "Generieke beeldscherm"
Option "DPMS"
HorizSync 30-83
VertRefresh 56-75
# V-freq: 56.00 Hz // h-freq: 60.85 KHz
Modeline "1680x1050" 135.32 1680 1752 1920 2224 1050 1050 1052 1086
EndSection

I've been playing with ubuntu since last year, reinstalling it over and over again, whenever I screwed something up and didn't know how else to get it right again
For some reason the screen did look perfectly sharp sometimes, but afther reinstalling again with the same settings it didn't

[zedfrugnug]

Bump

Does anyone know if this (impossebility to select correct refresh rate and unsharp screen) might be a problem with the nvidia-drivers or a bug in Ubuntu?

I'd like to know , because If it's a bug I'd like to file a bug-report.