I have a relatively new Powerspec computer (i5 quad core processor, about a year or two old) and just grabbed a new relatively inexpensive ($40?) graphics card. It has 1 DVI, one VGA, and one HDMI output.
I have two (different type) monitors plugged into the DVI and VGA slots, and they work great. However, I cannot seem to be able to get a third monitor in the HDMI slot to work. I can see the monitor (and monitor info) show up in display settings. However, if I try to switch the monitor to 'on' and click apply, nothing happens.
Anyone have the slightest idea what the problem might be? (It's a Radeon graphics card FYI; if I remember right I think it was the Radeon 4200?)
Best Answer
Sorry, based on the information in your question your card doesn't support three monitors.
The AMD/ATI technology for driving more than two monitors from the same card is called Eyefinity, but it is only supported on certain cards, see AMD's Eyefinity FAQ.
In brief, you need
The DisplayPort must be used for the third monitor.
In addition, AMD does not officially support Eyefinity on Radeon cards for Linux yet. Drivers exist, so with the proper combination of cards and monitors it can be made to work, but there are some limitations.
See also the question 3-monitor graphics on Linux on superuser.com.