Re: [gentoo-user] Radeon 9200/Xorg refresh rate

[Holly Bostick <motub@planet.nl>]

Mark Knecht schreef:
> On 11/17/05, Michael Kjorling <michael@kjorling.com> wrote:
> 
>> -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1
>> 
>> I have a ATI Radeon 9200 graphics card (lspci says ATI
>> Technologies, device 5940, rev 01) which currently drives my
>> monitor at 48.5 kHz 60 Hz 1024x768 using x11-base/xorg-x11-6.8.2-r4
>> and the "radeon" driver. I would like to raise the refresh rate to
>> 75 Hz. How do I do that?
>> 
>> Various Google searches have turned me up empty, except that
>> possibly the answer lies in the ModeLine used. Is that correct and
>> if so, what values would I need to tune to adjust the refresh rate?
>> 
>> 
>> /etc/X11/xorg.conf says that the vertical refresh rate is "50-90"
>> Hz.
> 
> 
> Generically modeline is the path to doing this. (I think...) I've
> done similar things using this site:
> 
> http://koala.ilog.fr/cgi-bin/nph-colas-modelines
> 

That's a good suggestion, but what all the replies so far seem to miss
is the fact that refresh rate is a *monitor* setting, not a video card
setting (although, because the monitor is a part of the X server-- along
with the video card, mouse, and keyboard-- the possible refresh rates
are also set in xorg.conf).

So the possible refresh rates for any given resolution rely on the
monitor's capabilities, not those of the video card.

>From my own experience, this can sometimes be tricky, depending on the
monitor. For example, my monitor is a 17" Eizo F550i-W. From the Eizo
site (I don't have a manual, as this was a hand-me-down from an office
that was upgrading), I found that the monitor is capable of 1280x1024--
but only@60, which many people find uncomfortable.

That's not the problem, though, if I want to use 1280x1024 (which I do);
the problem is that Eizo lists their monitor under both Windows and X,
meaning that they provide drivers for it, which I can use by selecting
the monitor's manufacturer and model during setup (under either Linux or
Windows). Except that the manufacturer-provided drivers are *limited* by
the manufacturer, to the "optimal" resolution of 1024x768@75.

So under either Linux or Windows (when I was still using Windows), I
could not use the manufacturer-provided drivers for the monitor, if I
wanted to use a resolution of 1280x1024-- that resolution was not
available, because the monitor only displays that resolution at 60Hz,
and Eizo doesn't want me to use a 60Hz resolution.

The only way I am able to set my desktop to 1280x1024@60 is to not use
the manufacturer-provided driver; under Windows I used "Generic VESA
1280x1024", and under X I must set my Horizontal and Vertical refresh
ranges manually (provided on the manufacturer's site, or in a manual, if
I had one). Under X, as long as the ranges are set correctly, X knows
that the monitor can display at 1280x1024, and sets the refresh to 60
automatically for that resolution (because the ranges I've given "tell"
it the correct combination of possible resolutions and refresh rates
that can be displayed).

The point being, you need to know your monitor's specs. Is it in fact
capable of displaying 1024x768@75? If so, the same place that told you
that should tell you the refresh ranges of the monitor. Plug those into
xorg.conf rather than whatever defaults might be there (which for me are
usually off by quite a bit, especially the horizontal range), and the
problem should sort itself after restarting the X server.

You can also do this with modelines, but I don't understand them
(meaning, I can't look at a modeline spec and know what it's trying to
do so that at need I could plug in my own), and so don't bother with them.

Hope this helps.
Holly
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