Problems with Screen Resolution

Duncan 1i5t5.duncan at cox.net
Tue Feb 1 00:01:44 GMT 2011


Wilson, Richard posted on Mon, 31 Jan 2011 20:29:18 +0000 as excerpted:

> Again my apologies, this is NOT a KDE issue [but] I thought I would
> post the working solution I have come up with

> My video adapter is a builtin Intel 82865G. The probe of this device at
> bootup reports back that it supports only 1024x768, 800x600 and 640x420.
> From what I read at Intel's website, that is incorrect, although I never
> did find a list of supported resolutions.

As you likely realize already, now, the kernel is handling mode-setting
now (KMS, kernel mode setting), and sets it originally at boot when it
loads the kernel graphics module for Intel.  My main machine runs a Radeon
and my netbook runs an Intel but I've not updated it recently, so I don't
know the newer Intel KMS details, but the problem is that it's detecting
things incorrectly whne it loads.  You should be able to supply the same
details to it using module-load or kernel command-line parameters that you
do to X using xrandr, below.  That way you have the same resolution at the
command line from boot, regardless of whether you load X or not.

> Using xrandr I got the following:
> 
> # xrandr
> Screen 0: minimum 320 x 200, current 1024 x 768, maximum 2048 x 2048
> VGA1 connected 1024x768+0+0 (normal left inverted right x axis y axis)
> 0mm x 0mm
>    1024x768       60.0
>    800x600        60.3     56.2 640x480        59.9
> 
> I had to use the cvt command to get the settings for a new mode:
> 
> # cvt 1280 1024
> # 1280x1024 59.89 Hz (CVT 1.31M4) hsync: 63.67 kHz; pclk: 109.00 MHz
> Modeline "1280x1024_60.00"  109.00  1280 1368 1496 1712  1024 1027 1034 1063 -hsync +vsync
> 
> I then had to enter the following both interactively (to test it) and
> then add it to /etc/gdm/Init/Default for reboots.
> 
> xrandr --newmode "1280x1024_60.00"  109.00  1280 1368 1496 1712  1024 1027 1034 1063 -hsync +vsync
> xrandr --addmode VGA1 1280x1024_60.00
> xrandr --output VGA1 --mode 1280x1024_60.00

FWIW the kde randr stuff (both in the display kcontrol/systemsettings
applet and in krandrtray) works for existing modes, but doesn't, AFAIK,
have any way of adding new modes, so they must be added as above using
xrandr commands.

Meanwhile, OT or not, thanks.  As I mentioned I haven't updated my
Intel-based netbook for some time, and on my AMD (both CPUs and Radeon
graphics) based main machine, I use KMS but the detection works just
fine, so while I've used xrandr on existing modes (before kde's randr
worked properly with Radeons with dual monitors as I have, making this
post at least a bit on topic), I've never had to actually add new modes
and the above was thus new to me.  I now have a better idea how to do
it, should that be necessary.  (I'd probably ultimately add it to the
kernel command line, as mentioned above, but either for temp-only use
or for testing modes with xrandr first, the above could be useful indeed!)

Hopefully when I upgrade the netbook, things go well, but at least
I've some idea what to do with xrandr to get the proper mode using it,
if the 2.6.37 or whatever Intel KMS drivers don't get it right, now!

That's one thing nice about mailinglists/newsgroups (I do my lists
including this one as newsgroups thru gmane.org).  You never know what
sort of even only tangentially related problem you might come across
a fix for, sometimes even before you know you have the problem! =:^)

But it's somewhat related here anyway, both because krandr only recently
started working correctly at all for many people with dual monitors, so
kde users /had/ to use xrandr or the like, and because it still doesn't
allow adding modes as you did above, so kde users /still/ have to use
xrandr or the like to add such new modes, since related kde took remains
unable to fill the entire role of the xrandr tool it's supposed to be
a graphical/kde replacement for.

-- 
Duncan - List replies preferred.   No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master."  Richard Stallman

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