I own a Radeon HD 7770 or 7790 (the exact number eludes). Since it was advertised as "Up to 6 displays supported" and had 4 graphics ports on the back of the card I mistakenly assumed that I could plug 4 random screens in and they would work. Since then a close read the fine print revealed that connecting a large number of screens likely needs a MST 1.2 hub. I purchased a MST 1.2 hub. My fourth screen remains black and unresponsive, and the software stack appears to be confused (xrandr listed only one of the two screens connected by the hub as available for configuration). The conclusion from this is that I am facing a software issue; further research suggests that the infrastructure needed for MST 1.2 is not in place. Is MST 1.2 support what I need to keep an eye out for? What needs to happen for MST 1.2 support? Is anyone working on this at the moment? Is there anything I could do to help? Cheers
MST support is not implemented yet. Dave started hacking on it, but as far as I know, it's not working yet: http://cgit.freedesktop.org/~airlied/linux/log/?h=radeon-mst-hacks
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