Foxconn X38A mainboard BIOS allows only increasing the voltage settings: you cannot lower them beneath the nominal values.

The processor core voltage can be raised up to +0.3875V with 0.0125V increment. All other voltages can be adjusted with a variable increment up to the following maximums: +1.491V for the memory, +0.38V for the chipset North Bridge, +0.424V for the chipset South Bridge, +-.56V for the FSB. You can select the desired value from the drop-down menu in the BIOS. All dangerously high settings are highlighted yellow, just in case.

All in all, Fox Central Control Unit section offers pretty good choice of options. Now the last thing we need to check out is the Hardware Health Configure page:

The section allows monitoring two temperatures, rotation speeds of three fans out of four that can be connected to the board. You can also monitor processor Vcore, Vmem, chipset North Bridge voltage and major voltages from the system PSU.

I cannot believe that anyone would ever need to disable monitoring functions, but if you do, there is H/W Health Function option for that matter:

You can formally lock the rotation speed of two fans at a certain value or let the mainboard adjust their rotation speed automatically depending on the temperatures. However, in this case it doesn’t really work: this option is not functional for fans with three-pin connectors.