1) The SeaSonic has two PCIe connectors one one cable. Don't use two on one cable. You should have 4 connectors plugged into the power supply itself (plus mother board and molex connectors). That means you will have 8 PCIe connectors use only one from each pair.
That did the trick, thanks. The SeaSonic cable has 6 separate 12V lines coming out of 1 modular connector, which splits into 2 separate PCIe connectors with 3 12V lines each, so I had assumed it would be ok (the 12V lines are not shared). But apparently there is a power limiter in the individual output connectors coming from the PSU.Figured it would be something like that. Glad I could help. Of course it helps that I had the exact same PSU and no problems.
Also I think KnC has been saying not to use the double plugs on pcie cables as well.
correct, albeit rather slyly after bitcoinorama claimed it would not/could not cause 'issues' on october boards.
around the same time as the 8 vs 4 VRMs debacle.