Comment 14 for bug 330906

Trevor: I can see an interesting difference here:

8.04:
VESA(0): Configured Monitor: Using hsync range of 31.50-36.48 kHz
VESA(0): Configured Monitor: Using vrefresh range of 50.00-60.00 Hz
...
(II) VESA(0): Attempting to use 56Hz refresh for mode "800x600" (114)

8.10:
VESA(0): <default monitor>: Using hsync value of 36.48 kHz
VESA(0): <default monitor>: Using vrefresh value of 60.00 Hz

8.10 seems to be insisting on a *single* vrefresh value of 60 Hz. I don't understand why it would do that. I've always seen the values for monitors expressed as a *range* of valid values.

8.04 uses a refresh rate of 56Hz, which is within it's range of 50-60. Perhaps 8.10 can't use the same timing because it will only accept modes of exactly 60 Hz.

I expect you *can* work around this problem, if you don't mind editting xorg.conf manually. You can specify the vrefresh and hsync ranges of your monitor manually, using the values from 8.04. I.e.

Section "Monitor"
 Identifier "Configured Monitor"
        HorizSync 31.50-36.48
        VertRefresh 50.00-60.00
EndSection

If you can, try to look up the values for your monitor. They should be on the back of the monitor, or in a manual. Or you may be able to find the figures online. V-refresh should have "Hz" on the end, H-sync should have "kHz".

My suspicion is that your monitor EDID (automatic configuration) doesn't provide these values directly. So X probably has to guess, or use some defaults - and this has changed between versions. Ironically, I would suspect the defaults were changed to increase compatibility with timing-fussy LCDs when using the Vesa driver :-D.