I have a video card with six mini display port outputs, and was hoping to use MST splitters to get Xorg to extend my desktop across more monitors than outputs on the card. However, when using xrandr to drive more than six monitors, I am told that it "cannot find crtc for output DisplayPort-4-1-1." Looking at xrandr --listproviders, I get the following.

Provider 0: id: 0x8d cap: 0xf, Source Output, Sink Output, Source Offload, Sink Offload crtcs: 6 outputs: 30 associated providers: 1 name:PITCAIRN @ pci:0000:04:00.0

Noticing the 6 CRTCs, I am somewhat concerned I will not be able to achieve what I want. Is this possible?

1 Answer 1


No: Each CRTC is responsible for producing a single "stream" (scanout of the display buffer), and you cannot produce more streams than you have CRTCs, no matter how you distribute them over your ports.

You may be able to mirror CRTC outputs to multiple ports (if the driver supports it), but you can't produce different content on more monitors than you have CRTCs.

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