915resolution howto

Matthew Kuiken matt.kuiken at verizon.net
Thu Dec 14 16:16:12 UTC 2006

Gabriel Dragffy wrote:
> I removed 915reslution (purge) and did what you said. But my xorg.conf
> alread looked OK to me, after a reboot the screen came up 1024x768 res
> again. Have attached my xorg.conf which I hope could help you.

Just as a first check, in the first part of my /var/log/Xorg.0.log the 
i810 module reports its version as:
  compiled for 7.1.1, module version 1.6.5

One of my first problems was that xorg was not detecting my LCD 
correctly (This was way back in breezy, BTW.)  Look in
/var/log/Xorg.0.log for the lines:

(II) I810(0): Broken BIOSes cause the system to hang here.
               If you encounter this problem please add
                  Option "DisplayInfo" "FALSE"
               to the Device section of your XF86Config file.
(II) I810(0): Display Info: CRT: attached: FALSE, present: TRUE, size: 
(II) I810(0): Display Info: TV: attached: FALSE, present: TRUE, size: 
(II) I810(0): Display Info: DFP (digital flat panel): attached: FALSE, 
present: FALSE, size: (0,2059)
(II) I810(0): Display Info: LFP (local flat panel): attached: TRUE, 
present: TRUE, size: (1366,768)
(II) I810(0): Display Info: Second (second CRT): attached: FALSE, 
present: FALSE, size: (0,2059)
(II) I810(0): Display Info: TV2 (second TV): attached: FALSE, present: 
FALSE, size: (0,2059)
(II) I810(0): Size of device LFP (local flat panel) is 1366 x 768

Here we are just checking to see that the video card correctly sees your 

A bit later in the file I have a section that looks like this:

(II) I810(0): Generic Monitor: Using hsync range of 43.89-48.51 kHz
(II) I810(0): Generic Monitor: Using vrefresh value of 60.00 Hz
(II) I810(0): Not using mode "1366x768" (no mode of this name)
(II) I810(0): Correcting stride (1368 -> 5504)
(II) I810(0): Increasing the scanline pitch to allow tiling mode (1376 
-> 2048).
(--) I810(0): Virtual size is 1368x768 (pitch 2048)
(**) I810(0):  Built-in mode "1360x768"
(**) I810(0):  Built-in mode "1024x768"
(==) I810(0): DPI set to (75, 75)

I am betting that if you find this section, it will say something about 
1280x800 being out of sync range, and falling back to 1024x768.  Using 
the command below:

$ gtf 1280 800 60

   # 1280x800 @ 60.00 Hz (GTF) hsync: 49.68 kHz; pclk: 83.46 MHz
   Modeline "1280x800_60.00"  83.46  1280 1344 1480 1680  800 801 804 
828  -HSync +Vsync

We can see that hsync for 1280x800 is outside the range given for 
Generic Monitor.  To fix this, we will try to add the following two 
lines to your xorg.conf in the Monitor section.

	HorizSync	29-50
	VertRefresh	30-70

The reason my monitor does not require this is that my display at 
1366x768 fits in those generic monitor values, while yours falls outside 
those ranges.  Adding these lines to the monitor section tells xorg that 
the monitor can handle different rates.  The important thing for the 
ranges is that they encompass the range that you are trying to display. 
  In the case above, I used 29-50, as 29.4 is 640x480, and 49.68 is your 

If this does not fix your problem, please post your Xorg.0.log.  If it 
does fix it, please let us know.


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