The BIOS setup of the X48T is identical to the X48-DQ6, which makes sense given that the only real change to the board is the type of memory used. The voltages for the memory are different, however the location of all the overclocking options remains the same.
Host Frequency: 100MHz to 700 MHz in 1MHz increments
PCI Express Frequency: 100MHz to 150MHz in 1MHz increments
DDR3 OverVoltage Control: +0.05v to +2.55v in 0.05v increments
PCI-E OverVoltage Control: +0.05v to 0.35v in 0.05v increments
FSB OverVoltage Control: +0.05v to +0.35v in 0.05v increments
(G)MCH OverVoltage Control: +0.025v to 0.375v in 0.025v increments
CPU OverVoltage Control: 0.83125v to 2.35000v in 0.00125v increments
Pressing into overclocking and our X48T-DQ6 board manged to get only a few MHz higher than the ASUS P5E3 Premium motherboard; a maximum of 569MHz FSB. Also note that this is an early BIOS for the board. GIGABYTE are currently working on new revisions to help increase performance and overclocking.
Important Editor Note: Our maximum overclocking result is the best result we managed in our limited time of testing the motherboard. Due to time constraints we weren't able to tweak the motherboard to the absolute maximum and find the highest possible FSB, as this could take days to find properly. We do however spend at least a few hours overclocking every motherboard to try and find the highest possible overclock in that time frame. You may or may not be able to overclock higher if you spend more time tweaking, or as new BIOS updates are released. "Burn-in" time might also come into play if you believe in that.