I feel pretty confident about it, since it shows up in the PCIE device tree but is not able to be recogniezed as a gpu. Furthermore, i tested different GPU configuration. Quadro + Tesla, GTX + Tesla, ... and de PSU supplies enough power corresponding rail. But my confidence might be the result of a lack of other clues.
I thought that i played around with enableing and disableing it during my last test run, but i will do it again.
Yes, its a dual GPU card and this was one of the reasons why i like the k80 so much. I used it a lot in rented server hardware and wanted to play around with one in my workshop The connected PSU and the GPU connected rail can supply engouht power to the GPU. Furthermore I will lend me a bigger PSU from a friend next week, so i can completely cross this from my list of possible reasons.
Thank you, this is my priority, too