Marquette University

Department of Mathematics, Statistics and Computer Science

Wim Ruitenburg's MSCS 206 linux learning 971101

We put warrior on line, split the screen output signal to go to both the monitor and the big screen projector, log in, and run X by typing startx A low resolution version of X appears on the screen, we guess about 640 by 480. This resolution was installed last time. Now we want to install the best possible resolution that our monitor offers.
As sources of information we have the file XFree86-HOWTO.gz in directory /usr/doc/faq/howto the file Modeline.gz in directory /usr/doc/faq/howto/mini and the manual from the manufacturer that comes with our monitor. Electronic files that are gzipped (with names ending in .gz) can be read with the less command by, for example, typing less XFree86-HOWTO.gz
The common command for installing X is XF86Setup. Run XF86Setup. Select the generic XF86Config setting (answer no to the first question). First hit <enter> until we are in the mouse select window. Use the tab and <enter> keys to select our PS/2 mouse in 3-button mode, and apply. Warning: During this phase we are not allowed to move the mouse or press its buttons! The mouse works. It has only two buttons, left and right. The middle button is simulated by pressing left and right at the same time. Second, we select our video card. This information can be found beforehand by typing SuperProbe. If you forgot, abort and do SuperProbe now. On our PC it gives us First video: Super-VGA Chipset: Matrox Millennium (PCI Probed) RAMDAC: TI ViewPoint3026 24-bit TrueColor DAC w/cursor,pixel-mux,clock (with 6-bit wide lookup tables (or in 6-bit mode)) So (rerun XF86Setup, and) as `card' select Matrox Millennium from the card menu. Third, we must select a monitor option. For now select the top version from the monitor menu. It doesn't give us the highest resolution, but it will work. Save the settings. Run startx. We have a working version. (As an aside, it looks very nice on the big screen projector.)

The installation just performed creates the file /etc/XF86Config. Each time when we run startx, the program looks at this file for its configuration information. We want to run X on our monitor in the best resolution possible. SuperProbe tells us that we have an SVGA monitor, and the manufacturer's manual (Panasonic E15) has a timing chart that lists its maximum resolution as 1024x768. There are two ways to get /etc/XF86Config upgraded to this better resolution. First, XF86Setup has the option to let you experiment with monitor settings manually, until a nice screen appears. In our case we didn't get very far with that. The second option, our current choice, uses the manufacturer's manual and the file Modeline.gz mentioned above to edit the /etc/XF86Config file `by hand.' We use a standard text editor (in this case vi) to look at /etc/XF86Config, and then modify it below. The first and crucial step will be adding a new `Modeline' immediately in front of the existing ones. An example `Modeline' looks like this: Modeline "640x480" 31.50 640 656 720 840 480 481 484 500 -hsync -vsync What do these elements mean? The manufacturer's manual (Panasonic's PanaSync E15) contains the following table related to the high resolution setting: VESA 1,024x768 75 Hz

DOT CLOCK	78.7500 MHz
fH	60.024kHz
Hor A-Total period	16.660 us	1,312
Hor B-Blanking time	3.657 us	288
Hor C-Sync width	1.219 us	96
Hor D-Back porch	2.235 us	176
Hor E-Active time	13.003 us	1,024
Hor F-Front porch	0.203 us	16
fV	75.000Hz
Ver A-Total period	13.328 us	800
Ver B-Blanking time	0.533 us	32
Ver C-Sync width	0.050 us	3
Ver D-Back porch	0.466 us	28
Ver E-Active time	12.795 us	768
Ver F-Front porch	0.017 us	1
Sync polarity (H/V)	Positive/Positive

These numbers play a crucial rule in editing /etc/XF86Config. From them we must somehow create a new `Modeline' that looks like Modeline "1024x768" A B C D E F G H I J K where A through K still have to be determined. Through comparisons with other settings in the manufacturer's manual, it is clear that the last two parameters reflect the sync polarities at the bottom of the table above, in our case positive/positive, so they must read Modeline "1024x768" A B C D E F G H I +hsync +vsync By checking out Modeline.gz, and by looking at the example Modeline above, we see that A is the dot clock in MHz, and B and F are the horizontal and vertical resolutions. So we have Modeline "1024x768" 78.75 1024 C D E 768 G H I +hsync +vsync By reading Modeline.gz we see that E = (dot clock) / (horizontal scan frequency) = (78750000/60024) = 1312. Note that this is exactly the number (Hor A-Total period). It is a good bet to guess I = (Ver A-Total period) = 800. (Modeline.gz says that I = (dot clock) / ((vertical refresh rate) * E) = 78750000/(75*1312)) = 800 which confirms our guess.) So we have Modeline "1024x768" 78.75 1024 C D 1312 768 G H 800 +hsync +vsync According to Modeline.gz the parameters C and D are chosen such that 1024 < C < D < 1312; they set the apparent width of the image on the screen by moving the left and right edge. Similarly, the parameters G and H are chosen such that 768 < G < H < 800; they set the apparent height of the image on the screen. One could experiment with these values to get a nice image. Instead we discover, by looking at some examples, that good values are obtained by adding the front porch and subtracting the back porch in the manufacturer's table from the bounding values.So set C = 1024 + 16 = 1040; set D = 1312 - 176 = 1136; set G = 768 + 1 = 769; and set H = 800 - 28 = 772. So the final modeline looks like Modeline "1024x768" 78.75 1024 1040 1136 1312 768 769 772 800 +hsync +vsync Create a backup copy of /etc/XF86Config, and edit the original file by adding this new Modeline right in front of the existing ones. We are almost done.

So far, with the new Modeline, we tell X what the screen can do in 1024x768 mode. We must now add that we want X to select this option when running startx. Again we must edit /etc/XF86Config. Since we have an SVGA monitor, we go down the file to where it says section "Screen" Driver "SVGA" Replace the first line Modes "800x600" "640x480" "640x400" "512x384" "480x300" "400x300" "320x240" "320x200" by Modes "1024x768" "800x600" "640x480" "640x400" "512x384" "480x300" "400x300" "320x240" "320x200" Save the changes. Type startx. It works. We also note that it doesn't look very nice on the big projector screen. The projector screen apparently prefers the VESA settings in 640x480 mode (see above) that we originally used.

Last updated: November 1998
Comments & suggestions: wimr@mscs.mu.edu