Hi guys,
first of all sorry for my English, I'm not a native... I've just build my new rig (specifications in the sign below).
Coming to the issue: at startup everything seems to work fine except that I can distinctly hear a weird ''click-clack" or "tic-tac" sound coming from MB, like some mechanical switch that operates. It's just on start-up, once, then everything works fine, the pc is stable (at the moment no OC, all default settings and no XMP enabled). Some stress test with OCCT and Furmark went ok, some hours of plaiyng The Witcher 3 and Dragon Age Inquisition without issues. It's just this ''tic-toc'' at startup. Should I worry about? Can be related with the NEC anti-pop relay that is indicated in the MB specification?
The first thing I did before even try to install the OS was to update BIOS to the last 1001 version by directly flashing from the motherboard. Then the OS installation and all the drivers (from both the included CD and the ASUS site for the updated ones). I've get rid of some errors due to drivers issues (wi-fi card, HD definition audio etc.) following your helpful suggestions in this forum and through the internet. Now it's just this issue and the unresolved one (as I was able to read in this forum) of the ACPI error 56, that is not causing any issue to me anyway, it's just on startup too.
I thank everyone can give some advice.

EDIT: Update - Seems my bad english was the faulty parameter in searching the internet 😞 I've just used the word ''clicking'' instead of tic-toc or similar, and got finally an answer 🙂 It's definitively the NEC relay. Nothing to worry about. See here: http://www.tweaktown.com/reviews/7276/asus-rog-maximus-viii-hero-intel-z170-motherboard-review/index...