Well, this will be the first english post I'll make. Fine.
As I've mentioned in other language posts, I've assembled a two-Xeon 2667v2 workstation with 256Gb ECC RAM on Asus Z9PE D8WS motherboard.
I've had a few unexpected quirks with it, but finally I made it stable working and all memory became accessible (which was the initial problem, caused, supposedly, by a videocard — I've replaced it and the problem was gone).
Anyway, the other thin that annoyed me until recently, was coil buzz.
This coil buzz (usualy called coil whine) sound was coming from somewhere around the CPU1 during some memory operations. I've tested CPU and RAM, and the «coil buzz» was happening not when CPU or RAM were tested, but when the RAM was released after testing.
I've spent quite some time pushing more voltage to RAM and CPU, thinking that this whine was caused by undervoltage of 256Gb of RAM, which was set to ≈1.5V by this mobo by default, which I thought was correct. What I finally found out was my RAM sticks were 1.5V/1.35V, and lowering the voltage to 1.35V did the trick — no more coil buzz sound.
This motherboard is good, but it requires you to know your hardware inside out.