D975XBX2 Current Processor Voltage vs CPU Voltage Override

I'm trying to OC my D975XBX2 with a E6600. I've gotten it up to 3.1GHz
(FSB 346MHz) with no problem. Fully loaded temp is at 50 C, stability
is good, and no voltage changes have been required. I changed the FSB
to 356MHz and I am basically stuck. I have upped to the MCH voltage to
1.575, FSB voltage to 1.4V, and increased the CPU Voltage Override 4
times and nothing has changed. Orthos will run for about 5 to 15
minutes and then either crash or get an error. Temps aren't any higher
then when I was at a FSB of 346MHz.

My question is whether I am really changing the CPU voltage. The
"Current Processor Voltage" field in the BIOS has not
changed from 1.325V and CPU-Z has not changed it's reading of 1.213V.
Should these be changing? I am using the latest BIOS revision of 2663.
The memory reference frequency is still sit at the default.

Thanks for any help.