I'm using a Lenovo x220i thinkpad, running crunchbang linux (which uses the openbox window manager). The laptop has a DP and VGA plug on the side.
Hooking up the DP and VGA cables and running
xrandr, I notice that the following outputs are available/active:
VGA1 DP1 LVDS1 <- the laptop screen
If I try to enable more that 2 (using any combination), then I get the error "cannot find crtc for output for [VGA1/DP1/LVDS1]"
What is crtc? How do I find out how many are available? Is it possible to add more in software or perhaps through a PCI card?