3*gtx 1080 ti cc+120 mc-1000
1*gtx 1080 cc+150 mc -1000
ubuntu 16.04 x64
cuda 8.0
driver: 384.59

EWBF 0.3.4b:

GPU0: 454 Sol/s GPU1: 672 Sol/s GPU2: 687 Sol/s GPU3: 679 Sol/s
Total speed: 2492 Sol/s
+-----+-------------+--------------+
| GPU | Power usage |  Efficiency  |
+-----+-------------+--------------+
|  0  |    153W     |  2.97 Sol/W  |
|  1  |    203W     |  3.31 Sol/W  |
|  2  |    198W     |  3.47 Sol/W  |
|  3  |    201W     |  3.38 Sol/W  |
+-----+-------------+--------------+

yours:

>  GPU0 Sol/s: 454.4  Avg: 454.4  I/s: 240.1  Shares/s: 0.000
>  GPU1 Sol/s: 684.6  Avg: 684.6  I/s: 365.5  Shares/s: 0.000
>  GPU2 Sol/s: 683.4  Avg: 683.4  I/s: 367.8  Shares/s: 0.200  ++
>  GPU3 Sol/s: 686.0  Avg: 686.0  I/s: 365.4  Shares/s: 0.000
   ==== Sol/s: 2508.5 Avg: 2508.5 I/s: 1338.9 Shares/s: 0.000