I have this LCD monitor that is a little broken, it works fine for digital DVI input, but does not work at all for analog. It used to work, but just after the warranty expired, it stopped working. The only computer that I had with digital DVI output is my macbook, and I have occasionally used it as a second screen for that, but the macbook lives in the living room and is rarely in the same room as the slightly broken monitor, so on Monday I ordered the cheapest video card I could find with digital DVI output from TigerDirect, and it arrived yesterday.
I immediately put it in the machine, hooked up the monitor and booted into my Fedora Core 6 linux. The second monitor showed nothing. Before I go on, here is a real quick HOWTO for other systems:
Mac OS X:
1) Plug in monitor.
2) There is no (2). Mac OS X will detect the monitor and use it, allowing you to change the settings etc. in System Preferences if you desire.
Microsoft Windows Vista Home Basic (the only windows system I’ve ever tried this with).
1) Plug in monitor.
2) Find the control panel for displays, and set it up to use the second screen.
Both pretty easy, though I prefer the Mac OS X way of automatically using the monitor by default. It is a rare occasion that one would plug in a monitor and not want to use it.
So, this is linux, no problem, there is a ‘Display’ menu item under System -> Administration. So I go there, set the nice GUI options for dual head, and reboot. What do I get? Not only does the second monitor not come up, but the first one goes to 800×600 resolution. Hmm. A bit of messing about later, and x.org starts but both monitors are now blank. Grr. At this point I googled (on another computer, of course, because the linux machine was effectively headless). And I discover that the auto configuration thing had added a ‘Screen 1′ line to the Device section of xorg.conf. So I sshed in to the linux machine and edited xorg.conf to remove that line (and clean up all the other crap that the linux magic GUI configuration tools had added), and finally got it working.
Section "Device"
Identifier "Videocard1"
...
BusID "PCI:1:5:0"
Screen 1 # This was bad, because the card only has one monitor attached to it
EndSection
So HOWTO for linux:
1) plug in monitor.
2) cry
3) goto 2.
Addendum:
If you need help setting up a dual head on your system there is a decent page at the gentoo wiki