[Bug 23508] CRT Refresh rate wrong

[bugzilla-daemon at freedesktop.org]

http://bugs.freedesktop.org/show_bug.cgi?id=23508





--- Comment #10 from Alex Deucher <agd5f at yahoo.com>  2009-09-02 10:55:10 PST ---
(In reply to comment #9)
> Hi,
> Quick response!...and thanks for the help.
> Both distro's Modelines are exactly the same.
> 
> Please excuse me for being dense, but what do you mean by perceived clock?

my monitors often report a slightly different refresh than the mode would
indicate.  So for example the modeline would indicate a 75 Hz mode, but my
monitor would claim it's actually 74 Hz or 76 Hz, etc.

> 
> I've tried the modeline that cvt (and your comment) suggests for 1400x1050 @85
> and that doesn't appear to have made any difference either.
> 
> Shouldn't the timings from gtf be used anyway though?  CVT didn't exist until
> 2003 (or so googling tells me) and my monitor was made in 1999 so wouldn't the
> two be incompatible?

Either should work.  The only thing that may be a problem is reduced blanking
modes.

> 
> I'll try upping the timings (maybe using gtf in the first instance?) gradually
> to see if I can get 85Hz out - but how far can I safely go before I'm at risk
> of frying my monitor's circuitry? ;-)

You can use gtf and adjust the timings as well.

It could likely be the pixel clock.  Some monitors are very picky about the set
of dividers used, even though the end result is the same exact clock.  Using
the pll dividers you can come up with multiple combinations that all get you
the exact same clock, but some monitors prefer some divider combinations to
others.


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