Not on the outside, unfortunately. The Gigabyte boards do have a 4-pin internal 12V connector, which is awesome, but I've yet to see an externally powered board with a strong DC-in connector in the wild let alone in retail.
As I am using a powered riser, the PCIe x4 slot stays within the 25W limit.
The other 40W the GTX 750 Ti needs under load are provided by the 12V AC adapter.
The fans remain on because of the 12V power supply can not be shutdown by the motherboard.
That´s normal. You must switch off the mains power.
On #2:
We don´t know, if the 12V In of the VGA card does apply 12V DC to the PCIe bus after the motherboard id shutdown.
If it does apply the 12 V to the PCIe bus this might cause such abnormal behavior.
Finally we must say, your DC power connection is not supported.
Each ATX PC standard powersupply does cut all 12V powerlines if the system is shutdown.
Do you have the same fan issue without the video card/extender installed?
What if I buy a GPU that only needs 25W max? Like the Nvidia GT 720? Claims to only need 19W. Could I just plug it in without any mods? Or with maybe an unpowered riser?
Do you have the same fan issue without the video card/extender installed?
Normally, an ATX power supply would provide power to the supplemental connectors only at system startup, then switch off when the system powers off. Only problem is that my power supply stays on all the time. By adding a relay that triggers when power is provided by the PCI-E bus, the graphics card is switched on at the same time the rest of the system is. This relay also provides power to the PCI-E connector of the GTX 1060 via a modified PCI-E cable that isolates the motherboard's 12V rail from the 12V coming from the power supply.