Driver thinks it's inactive and forces it to 2D-mode clocks? Would a dummy plug help?
what do u mean by dummy plug? how to tell the driver to activate the 3rd gpu ?Might be your extender? Have you tried switching the extender to the other vcard?
i did switched them up, so its not the extender issue, i bought 15.... so i tried it out, it was a painful 5hrs journey 