Re: XPS-15-9570 (Bios 1.7) -
I'm not sure this is the same as your issue but when connecting a WD16 dock the Temp6 goes from ~38C to 50C on Temp6 in HWInfo. Fans start when it hit around 42C which is way to early in my oppinion. My guess it is the PCH chip but thats just a guess from reading other ppl's observations.
I just get the feeling that Dell programmed the fan curves to start the fans on too low temps. With the XPS 9570 hardware design it's impossible to get a silent computer with those fan curves.