The risers i have is version 008s , all three options are available - 6pin / sata and molex.
So i hook up my cards with with PCIe connectors and the risers with molex ( have two cables with 4 molex connectors) 3 risers per cable?
Just my limited experience with 3 rigs (6-9 gpus each) and some friends experiences...the most risers I will power with molex is 3 but if I have enough cables try to limit it to 3. The SATA cables which i use a molex adapter to the riser I try to limit to 2. Keep an eye on things and feel the cables to make sure they are not getting hot.
The only components I have ever had an issue with are the risers and USB cables to them. Which makes sense because none of the risers are coming from name brand manufactures, there has been a shortage of them and hear many stories about bad risers. Out of my 24 risers only had 2 bad ones and 3 bad USB cables. A friend of mine had a USB cable start sparking which can be quite scary.
Even when you think you are reordering the same risers you may get completely different ones.
The 8pin to 2x 6+2pin cables are for powering your cards but I would only power ONE card with each cable. For 6 1060's a 850w PSU I do not feel is sufficient. I go by the rule of only planning to draw max 80% of the rated power so thats 680 watts for an 850w PSU.
Your base computer will most likely draw around 130-150w, 1060's draw 120 watts each OOTB (if i remember right). I undervolt mine to 95 watts, some people go lower but my experience with my cards is they were more stable long term at 95w. That puts you at 720 watts, which isn't bad the problem you come into is the number of PCIe cables. This was a real pain figuring this all out with my three rigs trying to buy PSUs when there was a big shortage and increases prices.
