On my GPU there are 3 HDMI ports and one DP. 

From the first HDMI to the DP, let's assume this numbering of HDMI ports: 1, 2, 3. 

I noticed that the HDMI 3 doesn't work ("no signal" on monitor). 

I sent the GPU on RMA. I received it today with the description "all HDMI ports working". 

Long story short: 

When the GPU is connected to the upper PCIE slot (PCIE2) the HDMI 3 doesn't work. 

When the GPU is connected to the lower PCIE slot (PCIE4) the HDMI 2 AND 3 do not work. 

Any ideas? 

And last, but not least - the double post/boot problem is present again - I didn't do any software nor hardware changes. It just reappeared. 

The update specifically addresses an issue with the Wireless AC functionality of the AC model boards. 

What I did was the following. 

I plugged everything (except the CPU) out. Then I connected the fans and only the Samsung 960 EVO. 

1. DISKPART > CLEAN. 

And freshly installed Win10... again -.-' (hate setting single app/setting again) 

After the installation, and updateing everything that "Windows Update" offered, I installed only the nVidia drivers (latest), and AMD chipset drivers from the official sites. 

Then I installed the RestartToUEFI app, MSI Afterburner, AIDA64, Chrome, and finally connected the internal Samsung 850 EVO to a SATA port. 

Now the PC works like it is supposed to - transfering files now doesn't "kill" the WiFi... and transfer speeds from external USB3.0 HDD to internal 850EVO go up to 159 MB/s - which is (afaik) perfectly normal transfer speed (?). 

I'm leaving it like this now... not installing a single app for a few days. No JRE, no updateing DirectX, I'm not even entering Microsoft credentials (because it will pull all my Windows settings back from the server). 

Then in a couple of days slowly "building" it up again, while in the meantime watching over the performance... 

Fingers crossed that the OP problems are gone... wish me luck :)

EDIT: About that BETA 4.61 BIOS - for me also is showing only on X370 Killer SLI/ac, not the "normal" (non AC) version. 

Thanks!

It is listed for Killer SLI AC, not for the non AC model.