VESA modes

[Jorge Almeida]

On Mon, 19 Mar 2007, Net Llama! wrote:

> On Mon, 19 Mar 2007, Jorge Almeida wrote:
>> I could use some help to understand what VESA standard modes are, and
>> how to use such beasts. From what [I think] I understood, the xorg server has
>> built-in knowledge about VESA modes. Hence, instead of writing a line like
>> ModeLine "1280x1024" 108.0   1280 1328 1440 1688 1024 1025 1028 1066 +hsync +vsync
>> in Section "Monitor" of xorg.conf, and then writing
>> Modes "1280x1024"
>> in Section "Screen", SubSection "Display",
>> one could simply write the latter, because the above modeline happens to
>> be one of the VESA modes.
>> What confuses me no-end is that the label "1280x1024" is associated with
>> several modelines, corresponding to different refresh rates. So, how
>> does the server know what to do? In KDE, one can choose a frequency in
>> the Control Panel, but that must be a front-end to something more
>> basic...
>
> X has its own built in modes, which are separate and unrelated to VESA
> modes.  The X driver that you're using will determine which modes get
This is what I meant (from the xorg.conf man page):
 	The  Identifier entry specifies the unique name for this monitor.  The Monitor section provides information about the specifications
 	of the monitor, monitor-specific Options, and information about the video modes to use with the monitor.  Specifying video modes  is
 	optional because the server now has a built-in list of VESA standard modes.  When modes are specified explicitly in the Monitor sec-
 	tion (with the Modes, ModeLine, or UseModes keywords), built-in modes with the same names are not  included.   Built-in  modes  with
 	different names are, however, still implicitly included.

> validated, and how they are named.  Generally speaking, starting X with
> the following command:
> startx -- -logverbose 6
>
> will show you alot more information about the mode validation process.
> The X driver that you use will determine whihc information appears.
>
OK, this is just a piece of that information:
 	(II) NVIDIA(0):   Validating Mode "1280x1024":
 	(II) NVIDIA(0):     1280 x 1024 @ 60 Hz
 	(II) NVIDIA(0):     Mode Source: VESA
 	(II) NVIDIA(0):       Pixel Clock      : 108.00 MHz
 	(II) NVIDIA(0):       HRes, HSyncStart : 1280, 1328
 	(II) NVIDIA(0):       HSyncEnd, HTotal : 1440, 1688
 	(II) NVIDIA(0):       VRes, VSyncStart : 1024, 1025
 	(II) NVIDIA(0):       VSyncEnd, VTotal : 1028, 1066
 	(II) NVIDIA(0):       H/V Polarity     : +/+
 	(II) NVIDIA(0):     Mode is valid.
 	(II) NVIDIA(0):
 	(II) NVIDIA(0):   Validating Mode "1280x1024":
 	(II) NVIDIA(0):     1280 x 1024 @ 75 Hz
 	(II) NVIDIA(0):     Mode Source: VESA
 	(II) NVIDIA(0):       Pixel Clock      : 135.00 MHz
 	(II) NVIDIA(0):       HRes, HSyncStart : 1280, 1296
 	(II) NVIDIA(0):       HSyncEnd, HTotal : 1440, 1688
 	(II) NVIDIA(0):       VRes, VSyncStart : 1024, 1025
 	(II) NVIDIA(0):       VSyncEnd, VTotal : 1028, 1066
 	(II) NVIDIA(0):       H/V Polarity     : +/+
 	(II) NVIDIA(0):     Mode is valid.

There are other "1280x1024" that were not validated, which agrees with
the monitor documentation. However, the two modes above have the same
label "1280x1024". Near the end of the log file, there is the line:
 	(II) NVIDIA(0): Setting mode "1280x1024"
Now, what mode is this? (What refresh rate will be used? The KDE control
center offers the two choices 75Hz and 60 Hz. What would be the
lower-level way to choose?)
-- 
Jorge Almeida