Here is small entry about how to do Voltmode using onboard jumper and where is Vcore monitor points.

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o o o = ~1.11V
[o-o]o = ~1.25V

o[o-o] = ~1.35V

From my own experience I was able to switch Vcore on the fly. Provided image below will give you possible point where you can measure you Vcore using multimeter.