What do you mean "impossible voltages"? Try confirming that 1.54 is being fed with core temp our cpu-z.
Also, turn on "load line calibration" (reduces vDroop) and that might change things in your case. It will make the vCore more stable.
Finally, one person being able to boot that speed with 1.4v doesn't mean everyone will be able to do it. Chips are different, boards are different, etc...
Hope this helps!