I have a Z840 with a 1250w PSU. The HP store is selling the workstation as suitable for a dual gpu configuration giving the example of a dual M6000.
I've installed a GTX 1080ti on one PCie slot but i've only found three 6PIN PCI-e power cables. Most of graphic cards needs 8 pin nowadays so i had to buy an adapter.
Now that i want to install a second GPU (another GTX 1080ti) , there's only one 6PIN PCI-e left - given that they sell the workstation for a dual M6000 which requires 2x8 pin - HOW IS THIS POSSIBLE?
Maybe there is a hidden psu cable somewhere? 
This is very frustrating since i bought the Z840 with the 1250w PSU for the dual GPU configuration - should i use a molex to pcie adapter for my second card? i've heard those adapters should be avoided so i really don't know how to configure the dual gpu.
Any suggestion will be highly appreciated