Trying to connect a 3rd monitor to my desktop, I cannot activate it. I connect it with a VGA to HDMI adapter (the monitor is VGA, but the only slot left for it in the box is HDMI. I get cannot find crtc for output VGA-0 trying to activate it in arandr.

Any advice and insights?

Here's the xrandr output, which seems to correctly identify each of my monitors. Also looks like it recognizes HDMI, so I'm a little baffled as to the context of the error message: VGA-0 is perfectly working, and it is HDMI-0 which I'm trying to activate when getting that error.

$ xrandr
Screen 0: minimum 8 x 8, current 3286 x 1080, maximum 16384 x 16384
DVI-I-0 connected 1920x1080+1366+0 (normal left inverted right x axis y axis) 477mm x 268mm
   1920x1080      60.0*+
   1680x1050      60.0  
   1440x900       59.9  
   1280x1024      75.0     60.0  
   1024x768       75.0     60.0  
   800x600        75.0     60.3  
   640x480        75.0     59.9  
VGA-0 connected primary 1366x768+0+0 (normal left inverted right x axis y axis) 410mm x 230mm
   1366x768       59.8*+
   1280x720       60.0  
   1024x768       75.0     60.0  
   800x600        75.0     60.3  
   640x480        75.0     59.9  
DVI-I-1 disconnected (normal left inverted right x axis y axis)
HDMI-0 connected (normal left inverted right x axis y axis)
   1920x1080      60.0 +   59.9     50.0  
   1280x720       59.9  
   1024x768       60.0  
   800x600        60.3  
   720x480        59.9  
   640x480        59.9  

If it matters, it is a GeForce GT 730/PCIe/SSE2 graphics card, and if I disactivate VGA-0, I can entirely successfully activate the monitor connected to HDMI-0.


There are three GPUs called the "GT 730". It's likely you've got the variant that only supports two monitors at a time (despite having three connectors).

Another possibility, which I haven't been able to confirm, is that your card only has a single RAMDAC, and thus can only drive a single analog monitor at a time. This shouldn't be an issue, though, as HDMI doesn't carry analog signals, so an HDMI-to-VGA converter should provide its own DAC.

  • Many thanks. What might be a good replacement card? couldn't find where AMD Radeon specs can be browsed out there. – Matan Oct 7 '15 at 8:22
  • 1
    If you want raw numbers, Wikipedia's got a huge list of every GPU ever made, if you want a relative performance ranking without numbers, Tom's Hardware has one, and if you want a specific recommendation for given requirements, there's Hardware Recs.se – Mark Oct 7 '15 at 8:33
  • Thanks but what about plain manufacturer specs for Radeon, like the one you found for Nvidia above? looks like that is where it will explicitly say how many displays are concurrently supported, judging by the Nvidia case. – Matan Oct 7 '15 at 8:41
  • Cool about stack exchange hardware recommendations site, never knew about it! – Matan Oct 7 '15 at 9:08

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