Thanks for your answers.
I want to add some additional informations about my two Rigs.
The cards are limited to 65% powerlimit for max efficiency.
I only use one card per cable. / one cable per riser
The PSUs are:
Rig1: FSP Aurum PT 1200W with 8 PCIE-Connectors
Rig2: Corsair HX1000i with 8 PCIE-Connectors.
This week i will also switch from a wooden Rig to a aluminum one.
Don't use Sata to PCIE in general. Satas cannot provide enough power without overheating and melting (been there and done that).
If you are planning on powering on GPU from two SATA cables off of the PSU then you may have a better chance.
But the general rule of thumb is never use SATA cables.
PCIE to PCIE only and you will be safe.
Yes I dont want a melting SATA-connector for sure.
But how much power will be drawn by the PCIE-Slot with GTX 1060 (75W by powerlimit) or GTX 1070 (100W by powerlimit)? Are there any measurements available?
Two cables per card isn't possible due to the fact that the PSU doesn't have 8 PCIE-cables so I can't use 2 cables per card. One cable but 2 SATA connectors per Riser is possible. PCIE to PCIE doesnt make sence, because if I have enough PCIE-Connectors, i dont need adapters
The problem with SATA connectors is they are not intended to deliver a high amp 12V load. There is only a single 12V wire that's also typically a smaller gauge than cables for PCI-E. Spreading the load over two connectors is better than using a single SATA connector, but if you do, connect the dual splitter connectors to the same SATA cable on the PSU and only use one riser per cable.
Using 4-pin Molex and PCI-E cables is a better choice. On modular PSU's the SATA and 4-pin Molex ports are often interchangeable and you can order extra cables from the manufacturer or on Amazon.
Very good idea with the additional cables. I didn't consider to buy additional Cables yet.
In general I have two Rigs with the same "problem".
I hope both PSU-manufacturers sell extra cables for these PSUs.
The question is also how much power each card will draw over the riser...
A GTX 1070 with a reduced power limit and 100W max consumption can be fully provide the energy by its 8-pin PCI-E connector - But no one knows how much will drawn over the PCIE Slot and how much over the power connector of the card. Same question ...
At first i will change the 1SATA-6pPCIE adapters to the 2SATA-6pPCIE adapters. One cable per Riser!