I recently bought j4105-itx board for my new silent pc. And while assembling it ,dropped a screwdriver in there  it was fortunate for me i guess, 4 smd elements was destroeyd in ddr VRM, most important - feedback resistors. Well, its not a problem to replace them, i knew we need 1.2V, so i looked at another asrock board with same PWM controller, get apropriate values and soldered them in place. And i have 1.285V, insted of 1.200. Hmmmm, feedback point voltage exacly 0.600, wat is wrong, i wondered, checked my resistors, they was equal to each other at 0.1% acuracy.

Hmmm. Well, i looked at another asrock board again(j3455), ther is funy little network which connected to fb point, RCR and 2n7002 mosfet shorting it to ground, all of that is controlled from multycontroller, memory voltage regulation thru additional PWM. 

And with stock firmware of j4105 that circuit is always on! Its not that big a deal actualy, it do not boost voltage to danger level, ~5%.

But after i updated the firmware to the latest avaleble on product page(1.40), my voltage get to nominal 1.200V, as they should be. Too bad that issue is not mentioned there. 

I have to do manual update, UEFI internet update utility was not able to find anything, but after i downloaded and unpacked files to flash drive, instand flash found update file and flashed it with no problems.

Funy but i do not have manual memory voltage control in UEFI, manual states that it should be at "advanced chipset" menu, nop, nothin there. Second misslead is memory - system working fine with single 2GB memory module, while manual say it should not. 

Well anyway, update ur firmwares, even if evreting is working fine at first glance.