Person may bought it with desperation after missing out on the RX 4 & 5 series cards.  lol

He is right I had all the main PSU powering the PCIe while server PSU power the 2 GPUs.  I notice the main PSU still draws under 400w even though it is powering the all the PCIe risers.

My setup is this
single 1080ti and all 4 PCIe risers on main that consume around 350w it should have been around 600w if those risers are doing highload work.
three 1080ti on the server PSU and the consumption peak around 700w.

another thing i found out if you don't connect the PCIe risers to server PSU.  its easy to turn on both PSU without timing.  you can turn on the server PSU first before main PSU. this leaves me thinking that the PCIe risers all it does power GPUs to connect and recognize while the PCIe 6 pin and 8 pin on the GPU gets use while on the load.

Even though I never run my 1070s at higher than 150.  I have a 1070 starts 180w and still run them under 130w.

not sure if you can leave one free but it should be one 8-pin and extra as optional.  8-pin provides 150w each and the 1070 is 150w max unless you free electricity and unlimited warranty.  you should never run 1070s at 122% tdp 24/7 mining.  most miners run 1070s at 120w having 2nd 8-pin does nothing.

Tbh i thought the same few months ago.  then i finally combine mining with trading to maximize profits.  mining alone isnt too good.

How are you guys finding these 1600w PSUs in stock?  I had to go with dual 1000w setup.  I put 3 1080ti per 1000w setup at 60% TDP.