Is Power usage /watts (if you changed TDP) the same on all cards then?
Do they show same voltage (mV) numbers in similar ranges or there are big gaps?
Remove all OC, reset to default settings. See if the are all equal or similar.
dont know what else 
Thanks juhub, I disabled P2 with nvidia inspector and the memory clock increased by 500 (from 5000 to 5500 with +0 on memory clock)
So are all sol rates almost equal now?
I’m not OP hehe. But I noticed some very small improvement on my cards, I had them falling under 700 at times (87% PL), it’s not falling under 700 after I disabled P2.
Okay, So I have 4x Asus GTX 1080 TI Founders Edition, Motherboard ASRock Z170 Extreme 4, Processor Intel G4400, Ram - 8gb, SSD - 120GB, two PSU - One is Corsair Cx750W and another one is LC Power - 750W, And 4x Risers from Amazon.
I connect two GPU’s, motherboard and SSD with LC Power and two GPU’s with Corsair.
I don’t do any overclock, only I adjust fan speed because it go up to 80 without adjustment.
Yesterday I install new beta update from Nvidia Graphic Driver version - 385.12 but I still receive even more lower hashrate.
So here I use ASUS GPU TweakII - GPU Boost Clock(MHz) - 1582, Memory Clock (MHz) - 11010, GPU Voltage (%) 0, Power Target (%) - 110, GPU Temp Target (C) - (-19), Frame Rate Target (FPS) - 0.
I use Nvidia Inspector to know Voltage 1st one have -1.063V, 2nd - 1.063V, 3rd - 1.044V, 4rd - 1. 1.050V, after working some time they go lower 1st - 0.950V, 2nd 0.794V, 3rd - 0.944V, 4rd - 0.813V.
So Here us Hasrates they power
GPU0: 65C with 337 Sol/s
GPU1: 61C with 177 Sol/s
GPU2: 68C with 582 Sol/s
GPU3: 73C with 583 Sol/s.
I don’t know how to adjust TDP settings.
Whaaaat? But how? Are they in a rig or in a case? Do you have extra fans?
It seems you may have some bad risers or not enough power draw.
If GPU0 AND GPU1 are the cards attached to the PSU that’s powering the mother board and CPU its most probable that your power supply is malfunctioning or is simply not enough for distrubuting power…
How are those GPU attached? Both with 2x 8pin?
Here is a screen of 3 1080ti that I’m testing right now (1080 ti aorus [gigabyte]):
All cards have +122 core, +400 mem and power limit at 90%, only one is set to 100+core and 300+ mem for temperature monitoring.
GPU0 → 69C | ~720 sol | 220-230W
GPU1 → 65C | ~720 sol | 220-230W
GPU2 → 62C | ~720 sol | 220-230W
Not final setting, they are laying on the ground hanging from books :P, no extra fans right now. Waiting for 1700W PSU for final setting → 8x 1080 TI
It is on RIG and recently I changed my driver version now one GPU start normally but won’t show on Device Manager,
Also I changed all riser with the new one, now also change that GPU riser again and still not show on device manager I don’t know why.
On my GPU there’s no space for two 8pin all, There’s only 1 6pin and one 8pin, also When I run the miner for the first time after restart they work fine like 600 Sol/s but after just a minute they go down.
How can I understand which GPU’s are working that low ? to understand which power supply they are connected?
With your settings they start working little bit fine but one gpu not started and temperature just go higher 75C with 80% fan
It depends from your motherboard, but usally GPU0 is the pcie lane on the top (closest to CPU) and GPU3 should be the one on the bottom. So if the 2 GPU’s that are closer to the CPU get powered from the PSU that is plugged to the motherboard it’s probably that PSU.
How do you power your risers?
I turned off all GPU’s and only use one, and again I have 582 Sol/s Hashrate, I can’t understand what is the problem? 
try to plug one gpu directly to the motherboard and check the hashrate, if there is a big difference then you got some bad risers.
Hello.
I have 6x 1080ti FE, ASRock H81 Pro BTC r2.0 with 2x EVGA 1000 G2. With 1 PSU and 3 cards it can’t start. Should I put more PSU power?
I dunno whats happening guys, you are soooo unlucky.
Let’s see if I can help, how are the 3 cards pluged to the motherboard? Did you try with 0 cards or only one?
Do you use risers? Is your PSU set to the correct voltage?
3 GPUs with risers to MOBO + PSU and SSD all on first EVGA 1000w. And 3 GPUs on the second EVGA 1000w. Do you think Power Supply is enough? The PC is starting only with 1 GPU.
Should be enough.
How are risers powered?
How are cards plugged? (8 pin?6pin? x2?)
Is the PSU that is not plugged in the motherboard “jumped”?
(EXAMPLE)
I have that cable to connect both PSUs. But now i have only plugged the first EVGA directly to MOBO. Worked with 1 GPU but failed with 2 and 3.
.********************
The Risers for the 3 GPU are connected with 3 Molex Cable which is going to SATA on PSU. 1st GPU is connected with 2 cables(1x8pin and 1x6+2 pin). 2nd and 3rd are both with 1 cable 6+8 pin.
Is your miner not in use ?? I have got same story on port 1.1 but only if I am doing something on pc hash drops around 100sols once left alone it goes back to normal hash rate
