Oh...you're using a Z series board, not a P board....that explains that.

Well anyway, what is the MAXIMUM multiplier you can do with PLL overvoltage DISABLED? x46, right?

You can't do x47, regardless of enabling or disabling it?
If that's correct, then the BIOS isn't working correctly.

BTW There's no such thing as a CPU that needs PLL overvoltage enabled for x42 (as that's the only way you would have a wall at x41 with it disabled).