3 monitors, 1 card
I would like to have three monitors using the same graphics card. I have researched this topic for some time now but I don’t seem to be able to find an answer. I don’t play games and I don’t need any 3D support. I use my computer only for development. My motherboard is an Asus P8H77-M/Pro, which has three PCIe expansion slots: 1x PCIe 3.0/2.0 x16 (blue), 1x PCIe 2.0 x16 (x4 mode, black) and 1 x PCIe 2.0 x1.
I use Linux Mint and Xfce – if that has anything to do with anything. I prefer HDMI output but I think DVI output is also sufficient or a combination of these two. Antti-Pekka Meronen While many graphics cards have three or more outputs, they don’t all let you use all three at once. Your motherboard is an example of this, it has DisplayPort, HDMI, DVD-D and VGA. Forget about the VGA as it will not output at the higher resolutions the graphics chip is capable of, but you can use any two of the other three. That leaves you with two choices. You can buy a high-end card with support for three or more monitors and drive them all from that card. Alternatively, you can buy a less expensive card that provides two outputs and connect two monitors to the motherboard and one to the card (or vice versa). As you only need plenty of screen space and not maximum performance, a high-end card would seem to be an unnecessary expense.
As far as the connectors are concerned, the three digital connections are largely equivalent so it doesn’t matter which you use. You can buy adaptors to convert between the various layouts or you can get cables that have different connectors on each end. A number of us here use the latter approach on a dual monitor setup, with one pure HDMI cable and one DVI to HDMI cable.
One thing to bear in mind when using HDMI is that it can also carry audio. As a result, connecting an HDMI cable to your motherboard will usually route audio over that cable and not through the speaker ports. If you want to continue to use separate speakers, you will probably need to change your mixer settings to direct the audio through the separate outputs.
Strange sudo behaviour
I am trying to change my laptop’s backlight brightness from the command line (I want to do it from a script eventually) like this: $ sudo echo 500 >/sys/class/backlight/intel_ backlight/brightness When I try this I get a ‘permission denied’ error, but if I use su instead of using sudo it works: $ su $ echo 500 >/sys/class/backlight/intel_ backlight/brightness $ exit
I don’t want to use su in my script, because that means it will ask for the root password, so why does one way work but not the other? Jason Brown It’s all about how the shell parses the commands that you give it. When you use redirection, the shell runs the command and then redirects its output, and all of that is done as the user running the shell. So first the script runs $ sudo echo 500 – this is run as your user but it calls the sudo command to get elevated privileges. Then it redirects the output, but this part is also running as your user, which is why you get the permission error message. In effect, you are running the wrong half of the command with root privileges. When you used su , you opened a subshell running as root so permissions were never involved.
So how do you send text to a file as root from a user terminal? The tee command sends its input to standard output and to a named file, and you can run it with sudo to deal with the permissions, like this $ echo 500 | sudo tee /sys/class/backlight/ intel_backlight/brightness
Note that tee overwrites any contents the file may already have, as with > . That is what you want here, but if you want to add to a file, as with >> , you must use tee -a . You really only want the output to go to the file and not be repeated in the terminal, so you can redirect that to /dev/null: $ echo 500 | sudo tee /sys/class/backlight/ intel_backlight/brightness >/dev/null Now you are using sudo and not su , there is