as long as the GPUs have thier own PCIe power, powering the risers shouldn't be a necessity.
keep in mind that the risers often limit the bandwidth of the cards, espescially if you use 1X risers as these will make GPU-intensive operations like games get really screwey with textures and artifacts freaking out all over the place. 16X risers should prevent this issue though (my GPU0 is on a 16x riser for gaming and the other 3 are on 1x risers for mining)
I have 16x risers.
I read a post of the ROG forums that said I should try turning the PCI gen to 2 in the Bios...and that worked for a while. I was able to actually have 2 cards visible in the device manager. Now I'm down to one again.
Maybe there's a special order the cards need to be added to get them to show up? I don't know...ASUS stuff is always weird and I'm going to try some more things before I RMA this board soon and never buy ASUS again.
Did you install the vid driver as many times as you have vid cards
Each card usually needs the driver(same driver,just reboot & install driver again) installed for it to be seen by the OS.
I will definitely try that, although at the moment the system is seeing the gtx 780 and the gtx 760. They both use the same driver.
Ah,Nividia...I always do a "clean install" (check the box while installing,under "custom install") of vid drivers too with nothing but the driver & HD audio & Physics.
Forget the 3D crap,its useless unless you actually found a use for it
Here is the best way to install Nvidia drivers:
http://www.overclock.net/t/989327/nvidia-clean-installhttps://forums.geforce.com/default/topic/462278/geforce-drivers/clean-driver-install/To boot in safe mode,type msconfig in the start button search field & go to boot tab & tick the safe mode box & apply.
You'll have to undo this later when you finish with driversweeper in safe mode,before you reboot,otherwise you just reboot into safe mode over & over & over
Be careful when running Driversweeper,DO NOT REMOVE CHIPSET DRIVERS,you'll have to do a full OS reinstall to fix that goofup