Further investigation into PCH voltage effects in qubes (strange finding)

[daltong defourne]

Setup:
Asus ROG Hero VIII motherboard
32 GB PC-3200 RAM DDR4
Skylake  core i7 6700k
adaptec 5805z RAID controller
vt-d enabled.
Nvidia GTX 1070 GPU
Double PSU config (500 w each)

A "store" VM with a RAID storage pcie device attached to it

a "USB-BOX" VM with a USB controller attached.

When PCH voltage is at ~1.125 the speed of copying a large file from RAID to a USB drive (attached to the store VM via qubes's block device attaching mechanism) is no more than 20 MB/s and transfer happens in notable "chunks" (transfer stalls for about a second every 5-6 seconds).
When PCH voltages exceeds 1.14 (let's get dangerous...) speeds of transfer from RAID to USB drive (attached to the store VM via qubes's block device attaching mechanism) reach 100MB/s and have no stalls.

I am wary of running PCH at voltage that high (wrote to ASUS support...) and would like to find out more about 1) why it happens and 2) whether it's normal