Hi Jabuzzard,
Thanks for your reply: Indeed, bios-wise the GPU's are supported; most in this thread managed to get multiple GPU's to function on the first 2 PCIe slots, and some also managed to get some GPU's to function on the rear PCIe edge slot via a riser connector.
Problem we are having is that we cannot get the rear PCIe Edge slot to become visible in the BIOS and we suspect the reason for this is that Dell deliberately disabled this PCIe Edge slot in BIOS version v2.10 for the C6220ii, as it normally isn't possible to connect the riser connector to the Edge slot in the C6000 chassis, whilst it is possible in the C8000 chassis (As an analogy: in the 12-bay version of the R510 Dell disabled the SATA ports at BIOS level as they didn't think anyone could connect a SATA drive to it (due to space considerations), however along came satadoms which did allow use of those SATA ports, yet Dell refused to re-enable the SATA ports in BIOS).
For this reason we specifically asked Dell beforehand whether they had disabled that Edge PCIe slot at BIOS level, and Dell claimed they hadn't, and Falanger his videos also show the Edge port popping up in his BIOS, whilst Falanger also appears to have flashed a C6220ii BIOS version.
So we don't really understand what our issue is, but the chance that we made a mistake with the power connectors is very small, as it just isn't that difficult: we just powered the riser as per how it should be (2 x 12V, and 2 x ground) and powered the K80 using an official K80 NVIDIA dongle (that converts "6 pin PCIe + 8 pin PCIe" to 8-pin CPU power) and our power budget is ample (1200W for 2 K80's + fans): it can't possibly be underpowered and the green indicator light on the K80's does switch on. So we have no idea why the Edge slot just wont pop up in our BIOS.
I will be at the data center this weekend and will make some photographs, but any ideas you have are much appreciated.
Kind regards, JJ