i810 vs. intel: frequency differences?

Adam Jackson ajackson at redhat.com
Fri Apr 13 17:10:20 UTC 2007


On Fri, 2007-04-13 at 09:39 -0700, Tom London wrote:
> Running xorg-x11-drv-i810-1.6.5-19.fc7, I've noticed that seem to
> drive different monitor frequencies for the same
> monitor/settings/xorg.conf.
> 
> Running on two different LCD monitors, if my xorg.conf says 'i810', I
> consistently get Horiz rate of 79.8kHz and Vert rate of 74.6Hz.
> 
> If I only change i810->intel and restart X, I consistently get Horiz
> rate of 83.0kHz and Vert rate of 77.8Hz (the last is above supported
> rate (~75Hz) for both monitors).

The X log, at least for the intel run, should show the exact timings
being sent to the monitor, as well as what the monitor reports for
capabilities.  That said, there could easily be bugs in the intel
driver.

> I've also noticed inconsistencies between the rates reported by my
> monitors and that reported by xrandr when I run with 'intel': xrandr
> reports Horiz is 80kHz (vs. monitor reporting 83kHz) and Vert is 75Hz
> (vs. monitor reporting 77.8Hz).

Rounding error.  Monitors are not particularly smart.

- ajax




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