On windows 10 x64 (without --enable-nv-hotfix)
1x1070 - 14.0-15.0
2x1070 - 10.0-10.5
3x1070 - 7.8-8.2
1x1050 - 5.0-5.2
On windows 10 x64 (with --enable-nv-hotfix)
1x1070 - 1.8-3.0
2x1070 - 1.8-3.0
3x1070 - 1.8-3.0
1x1050 - 5.0-5.2
On ubuntu 16.04 (with --enable-nv-hotfix)
3x1070 - 13.2-14.0 (core 150, mem 300)
4x1060 - 8.7-9.2 (core 100, mem 200)
5x1050ti - 5.3-5.8 (core 50, mem 0)
But what is your cpu, even if its HyperThreaded, use the number of physical cores it has. otherwise crashes or slowdowns happen. 1 core per card.