Hi,
I have an X99 Motherboard that I modded to allow bifurcating the last 8X pcie slot into two. This particular slot shares bandwidth behind a switch that routes half the lanes to an onboard M.2 slot hosting a Samsung 950 Pro. Limitations being you loose the last pcie slot when the m.2 runs at pcie 4x mode through the cpu which is a 40 lane 6850k. However after modding the bios of my motherboard and enabling a certain register inside the IntelSetup module I could now operate the M.2 at 4X and a second Plextor Nvme pcie card off of the last Pcie slot with the use of a bifurcated 4x4x riser card. The problem i am experiencing however is when the pcie bus is bifurcated, doesnt matter if card is connected directly to slot or not, sometimes randomly my plextor upon a reboot will be at 2.5 Gt/s operation as opposed to 8 gt/s mode. Not sure what could be cause of this except I have noticed that Lspci reports that only the first equalibration phases had completed successfully in that the 2nd and 3rd had failed. Most of the time it goes away after a reboot or driver reinstall. So if anyone can help i would appreciate it,
Thank you.