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Old 01-29-2008, 02:47 AM   #1
Registered: Dec 2007
Posts: 59

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Unhappy Dual head has mind of it's own; how to tell it which is primary monitor?

I am trying to set up a dual head system on a legacy linux fedora box (the legacy is the hardware, not the software, which is up to date). The problem is that Xorg has it's own muddled ideas about which head is which, and I can't seem to set it straight.

I have 2 video cards, an s3 virge and an mga g450. I have two vanilla, heterogenous monitors, one CRT, one LCD.

For physical reasons(office space) I want the LCD to be the primary monitor, on the left. I set up the system as one monitor, LCD into the MGA card, configure X, all is well.

Now remove that card, stick in the Virge, connect the other monitor, lather, rinse, repeat, all is well.

Now set up as a two monitor system. Configure the MGA and LCD as the primary, virge and crt as secondary. System comes up, and the CRT and the virge light up, LCD stays dark. Weird - the virge is the secondary monitor. Configure display, settings have reverted to probed defaults. Attempt to set up dual head, system sees TWO virge cards, no MGA!!?!

I have been 'round and 'round with this for some time. Sometimes the system sees the MGA card but always as the secondary, and I never get the second monitor. Now it tries to connect to the mga as a virge and naturally fails.

So, two questions:
- How to force the system to accept that MGA card as being on the primary monitor?

- How to unconfuse it about the existence of a second virge instead of an mga? I think they are related.

Some debug spew follows.



[riley@rwfedora ~]$ /sbin/lspci
00:00.0 Host bridge: VIA Technologies, Inc. VT8377 [KT400/KT600 AGP] Host Bridge
00:01.0 PCI bridge: VIA Technologies, Inc. VT8235 PCI Bridge
00:05.0 VGA compatible controller: S3 Inc. 86c325 [ViRGE] (rev 06)
00:06.0 VGA compatible controller: S3 Inc. 86c325 [ViRGE] (rev 06)
00:07.0 Ethernet controller: Lite-On Communications Inc LNE100TX (rev 20)
00:0c.0 Multimedia audio controller: C-Media Electronics Inc CM8738 (rev 10)
00:10.0 USB Controller: VIA Technologies, Inc. VT82xxxxx UHCI USB 1.1 Controller (rev 80)
00:10.1 USB Controller: VIA Technologies, Inc. VT82xxxxx UHCI USB 1.1 Controller (rev 80)
00:10.2 USB Controller: VIA Technologies, Inc. VT82xxxxx UHCI USB 1.1 Controller (rev 80)
00:10.3 USB Controller: VIA Technologies, Inc. USB 2.0 (rev 82)
00:11.0 ISA bridge: VIA Technologies, Inc. VT8235 ISA Bridge
00:11.1 IDE interface: VIA Technologies, Inc. VT82C586A/B/VT82C686/A/B/VT823x/A/C PIPC Bus Master IDE (rev 06)

[riley@rwfedora X11]$ cat xorg.conf
# Xorg configuration created by system-config-display

Section "ServerLayout"
Identifier "single head configuration"
Screen 0 "Screen0" 0 0
InputDevice "Keyboard0" "CoreKeyboard"

Section "InputDevice"
Identifier "Keyboard0"
Driver "kbd"
Option "XkbModel" "pc105"
Option "XkbLayout" "us"

Section "Monitor"
Identifier "Monitor0"
ModelName "Monitor 1024x768"
### Comment all HorizSync and VertSync values to use DDC:
HorizSync 31.5 - 57.0
VertRefresh 50.0 - 70.0
Option "dpms"

Section "Device"
Identifier "Videocard0"
Driver "s3virge"

Section "Screen"
Identifier "Screen0"
Device "Videocard0"
Monitor "Monitor0"
DefaultDepth 24
SubSection "Display"
Viewport 0 0
Depth 24
Modes "800x600" "640x480"

Last edited by RileyTheWiley; 01-29-2008 at 09:08 PM.
Old 01-30-2008, 12:31 AM   #2
LQ Guru
Registered: Mar 2004
Distribution: SusE 8.2
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Hi -

You actually just answered your own question:

1. X Windows will try to "autoconfigure" itself. It usually does a pretty good job :-)

2. However, if you don't like something, you can always hand-edit your Xorg.conf file and change it.

3. Better still, you can save multiple versions, and experiment with which settings you like best.

Here's a link with more information:
<= There are many similar "howto's" and tutorials for
configuring X, if you don't like this one. Just "Google"...

'Hope that helps .. PSM

If you get in trouble and mess things up so badly the GUI won't even come up problem! Linux lets you type <Ctl-Alt-F1>, <Ctl-Alt-F2>, etc etc to get a terminal login. Just log in as "root", copy back your last known good Xorg.conf, and restart X Windows.

How did things go with your USB "hot plug" question?
Old 01-30-2008, 01:58 PM   #3
Registered: Dec 2007
Posts: 59

Original Poster
Rep: Reputation: 15
Lightbulb Found it, thanks ..

The problem with the dual head was in the single head that was driving the computer: short circuit in the cranium.

In the first place, I had 2 virge cards in there, at least for a little while, which helps to explain why Xorg thought I had 2 virge cards in there, at least for a little while. In the second place, I had 2 video cards in there, and only needed one. The MGA card has two outputs, one of which I recognized as the standard VGA jack, the other was some square thing which I now know is a DVI-I jack. When the MGA was paired with a virge card, Xorg was strobing the DVI jack on the MGA and not finding a monitor, then looking for other heads, and finding one on the virge. When the MGA ran alone, it would check the "secondary" (VGA) jack and find my monitor.

Solution: Get a DVI->VGA cable adapter. Five bucks through Amazon.

Thanks for the reply. I will leave this for Google to find.



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