Re: Undefined video mode number: 314

[Stephen Powell <zlinuxman@wowway.com>]

I need to correct an earlier post.

On 2010-01-13 at 11:57:48 -0500, Stephen Powell wrote:
> Unfortunately, there doesn't appear to be a way to specify the
> video bandwidth of the monitor to the X Server, which is really
> how it should be done.

Oops, that is now no longer true!  There didn't used to be a way,
but now there is.

   Option   "MaxClock"   "110"

in the monitor section is the way to do it.  In your current
setup, it doesn't really matter because the video card's
maximum dot clock rate is lower than the monitor's video bandwidth.
Therefore, it is impossible to exceed the monitor's video bandwidth.
But if you ever use this monitor with another video card, one whose
dot clock can go faster than 110 MHz, that is the "right" way to make
sure that you don't overclock your monitor, rather than overriding
the DacSpeed in the video card section.  There is a "MinClock"
setting too.  According to the man page for xorg.conf, this
value is to be specified in kHz, but I think that that is probably
a mis-print.  Dot clock values have always been specified in MHz.

In summary, the governing equations for CRT monitors are as
follows:

horizontal_frame_length * vertical_frame_length * vertical_refresh_rate = pixel_clock_rate

   and

horizontal_frame_length * horizontal_refresh_rate = pixel_clock_rate

(This is assuming a non-interlaced mode.)  From these two equations,
a third equation can be derived, which is

vertical_frame_length * vertical_refresh_rate = horizontal_refresh_rate

These govern all the trade-offs in video modes.  As you can see from
the first equation, if you want a higher vertical refresh rate, you must
either use a higher pixel clock rate or a lower resolution.  These are
the laws of physics and you can't change them.

Also, after re-reading the series of posts, I now see why you said

> Less??

That first time.  You're right, the correct word in that sentence was "more".
Good luck and best wishes.