I can completely turn off any 1 of the 3 PSU's while the rig is mining and it will not skip a beat and continue mining shifting the load to the other psu's
So, only one power cable for the psu in the middle ? or all? for what aim in the end ?
No, you will overload the cable if all those GPU's end up trying to draw power through a single cable.
example on my 1200watt psu rigs, 6 x 1080ti's
3 cables to 3 x GPU's from PSU 1
3 cables to PSU 2 from PSU 1
3 cables to 3 x GPU's from PSU 3
3 cables to PSU 2 from PSU 3
So i have 6 cables running from the spare PSU daisy chaining the 2 other PSU's
I ordered this style breakout board from aliexpress for $1.90ea, i bought 50 of them at the time
I have boatloads of this BB and they are compatible with the Delta 2400w server PSU too, which made life easier in the farm.
There are also variants of these breakout board, which has a "on/off" switch - I prefer these types (I use both types).
These types are useful during troubling shooting and avoid physical power off at wall.
I have attempted the 19 GPU riser-powered rig using the Asus Mining Expert 19 GPU mobo, with 8xP106s and 11x470s (and 11x1060s), it took 2 x Deltas to work and exceeds 14A out of my 20A rail. I have dismantled these rigs due to power draw and limited power supply in the warehouse. To do hi-density rigs like this (for a farm) and the one Phil is evaluating, a better cabling and power planning is required, IMHO.
In the long run, this will be great for highest density, useful in farms. However, I have standardized 6 and 8-slot riser-less mobos in both my GPU farms.
Maybe, in the 3rd GPU farm project, I will go for ultra-density and that will need custom cabling and redo my power setup.
For now, my group's investments in 2018 are all ASICs... but that's another story all together.