FC2 - only 85Hz

[Jonathan Rawle]

Janis K wrote:

> it shows this:
> 
> "1024x768"  94.50  1024  1072  1168  1376   768  769  772  808  +hsync
> +vsync
> 
>>
>> The first number after "1024x768" is the "Pixel clock" in MHz. The
> formulas
>> connecting the different frequencies are:
>>
>> Horizontal sync = Pixel clock / HTotal
>> Vertical sync = Horizontal sync / VTotal
> 
> so my pixel clock shows 94.50 and xvidtune shows that HTotal = 1376 and
> Vtotal = 808 (is it in Hz?)
> and to calculate with the formulas i have this:
> 
> Horizontal sync = pixel clock / Htotal = 94.50 / 1376 = 0.068677325581...
> Vertical sync = Horizontal sync / VTotal = 0.068677325581 / 808 = 0.000085
> 
> is it so? I think I'm doing something wrong with these Hz/kHz/MHz ... I
> have no idea about this and I am terribly afraid to demage my monitor
> 

The pixel clock is 94.50 MHz = 94500000 Hz
(the correct units are shown in the xvidtune window)

If you want 100 Hz Vertical sync, you need
Horizontal sync = 100 Hz x 808 = 80800 Hz
(that's 80.8 KHz, so make sure your monitor can handle this!)

Pixel clock = 80800 Hz x 1376 = 111180800 Hz = 111.18 MHz

So replace 94.50 with 111.18 in your Modeline.

As long as you have the VertRefresh and HorizSync limits right in xorg.conf,
there shouldn't be any risk of damaging your monitor. If the new mode you
have defined is incompatible, X will simply choose a mode with a lower
refresh rate instead (i.e. it'll still be on 85 Hz) If that happens, try a
lower pixel clock.

Jonathan