Thursday, April 22, 2010

Ubuntu Lucid - Monitor Resolution check

My experience with Nvidia graphics card and iiyama 24 inch monitor has been good and bad with Ubuntu Lucid (beta).

Here I list a few steps to confirm that things are working as they should be. These might give you some clues if you are having intermittent 'out of range' messages in beta of Ubuntu Lucid.

From within Ubuntu Graphical desktop, click the display properties icon in the panel:

...and select 'Configure Display Settings' which will open a dialog box like this:

( System -> Control Centre -> Monitors ) will get you 'display properties' if your panel is missing the clickable icon.

During my earlier problems with getting a working display the 'Refresh rate' box showed 0Hz which is nonsense.

If you have your monitor manual to hand then you can check the 'Refresh rate' for the 'Resolution' to make sure that the systems own guesswork seems reasonable.

Now this Iiyama 24 inch B2403WS monitor has 1920x1200 Vertical Frequency listed as 60Hz.

( If you are not specifically told 'Refresh Rate' then use Vertical Frequency is a good guide as this Wikipedia article may suggest)

So refresh rate 60Hz looks okay to me.

( System -> Administration -> System Testing ) will give you some further information about detected resolutions (when you get to the appropriate test)

[ Technical Term here (feel free to skip what I say in this paragraph) ...Incidentally, if you feel like you need a figure for Video Bandwidth and cannot see it explicitly mentioned then look at the highest value of 'Dot Clock' and use that (162MHz in my case)  ]

In summary, most of what I can see for my monitor setup looks good :)

If you have upgraded your system then you may have a stored monitor configuration in your home directory. If so find the details in ~/.config/monitors.xml (my stored config is shown here):

My stored configuration has the important parts correct (rate 60) but looks a bit lacking for the fields vendor, product, serial.

It has been suggested that removing ~/.config/monitors.xml might help you overcome an 'out of range' message. You might want to keep a personal copy of monitors.xml (under a different name), as this file might be a way of tricking your system into using a fixed refresh rate if auto-detection continues to give you problems.

The poor guesswork in monitors.xml for vendor, product, serial might be because this file is two months old, and was perhaps generated in the Ubuntu Karmic install (which was on this machine before the upgrade to Ubuntu Lucid beta).

One question which is worth a look with any new graphic driver is how good are the Modeline entries that it is using?

Here is some information about the Lucid beta version of Nouveau and Modelines for my monitor:

What is of interest to me is the 'initial mode', and the Modeline which is the closest match to, what the graphical monitor configuration tool reported.

I have used the command 'cvt' to independently generate Modelines with which I can compare.

Looking at the results of the cvt command without --reduced flag generated ( 193.25 ), this differs considerably from my monitor printed manual listing for 1920x1200.
I would only use modeline output from cvt generated with --reduced flag.

This article is intended to act as a series of hints as to what extra information you might consult, if Ubuntu Lucid guesswork for your monitor is producing poor results or intermittent 'out of range' messages.

If you have an Nvidia graphics card and want to compare your /var/log/Xorg.0.log to help your analysis then here is a directory of sample Xorg logs.

In particular here is an example of an Xorg log where Ubuntu Lucid beta worked well.

Note to the people who code the monitor vendor names:

The Japanese company who make my monitor are (in lowercase) iiyama, when you uppercase the first i to become (I), it is sometimes then assumed to be an uppercase L, which might explain your entry in the monitor database.

Here is a link to a websearch that might verify things:
    websearch for monitor company

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