GTL Reference Voltages for Quad-Core Processors

FSB Termination Voltage:
The scale runs from 1.2V-2V in .02V increments. Again, the board overvolts the BIOS setting by around 0.03V-0.04V. We recommend that users do not exceed a setting of 1.56V (1.6V actual) for 24/7 use. As FSB is raised with a quad-core CPU, VTT also needs to be raised. Expect to use between 1.5V-1.6V for overclocks past 440 FSB.

CPU GTL Reference:
Available options are, 0.57x, 0.59x, 0.61x, and 0.63x. This function controls GTL reference voltage to both CPU die's simultaneously. This is not completely ideal as there are always mismatches in CPU fabrication and motherboard components that may require individual GTL voltage level adjustments for each CPU die. The only option of use here is 0.63x, which is actually mislabeled and closer to around 66-67% of VTT. Intel specification for GTL reference voltages is 67%. We probed the on-board voltages with a DMM to find out just how close ASUS is to the 67% mark of VTT.

Voltage Investigations
BIOS Set VTT Measured VTT BIOS set GTL Measured GTL 67% of VTT
1.50 1.53 0.63x 1.022 1.025
1.52 1.55 0.63x 1.036 1.038
1.54 1.57 0.63x 1.051 1.051
1.56 1.60 0.63x 1.065 1.072
1.58 1.62 0.63x 1.080 1.085
1.60 1.64 0.63x 1.090 1.098

The closest point to 67% on our motherboard for both CPU die is 1.54V (set in BIOS). Although the differences between actual GTL and Intel 67% specification seem small, fine control of the GTL voltages would have helped the board's overall stability when pushing past 450FSB with the Quad Cores. Each board will have a different level of voltage variance due to on-board component tolerances. In short, a 0.63x setting for GTL at 1.54VTT will not equate to the same measured GTL value on every board and may be adrift from the ideal 67% specification.

NB GTL Reference:
The scale runs from 0.49x to 0.67x in 0.02X increments. 0.67% worked best on our board and processors. We found that values lower than 0.67x caused lock ups and non-boot situations. Again, finer control options would have been nice and should be expected on a board in this price range.

We listed our BIOS settings below for a stable 450FSB run of the Prime95 torture test (8 hours 54mins passed), for those who are interested in this type of stability. Please note that component abilities do vary from board to board; these settings are only an approximate guideline.

450FSB Quad-Core BIOS Settings
CPU Feature
Ai Overclock Tuner [Manual]
OC From CPU Level Up [Auto]
CPU Ratio Control [Manual]
Ratio CMOS Setting: [8]
FSB Frequency [450]
FSB Strap to North Bridge [400MHz]
PCIE Frequency [110]
DRAM Settings
DRAM Frequency [DDR2-1199MHZ]
DRAM Command Rate [2T]
DRAM Timing Control [Manual]
CAS# Latency [5]
RAS# to CAS Delay [5]
RAS# Precharge [5]
RAS# Active Time [12]
RAS# To Ras# Delay [3]
Row Refresh Cycle Time [42]
Write Recovery Time [6]
Read To Precharge Time [3]
Read To Write Delay(S/D) [8]
Write To Read Delay(S) [3]
Write To Read Delay(D) [5]
Read To Read Delay(S) [4]
Read To Read Delay(D) [6]
Write To Write Delay(S) [4]
Write To Write Delay(D) [6]
DRAM Static Read Control [Disabled]
Ai Clock Twister [Strong]
Transaction Booster [Enabled]
Boost Level [0]
Voltage Settings
CPU Voltage [1.43125v]
CPU PLL Voltage [Auto]
North Bridge Voltage [1.61v]
DRAM Voltage [2.16v]
FSB Termination Voltage [1.54v]
South Bridge Voltage [Auto]
Loadline Calibration [Enabled]
CPU GTL Reference [0.63x]
North Bridge GTL Reference [0.67x]
DDR2 Channel A REF Voltage [Auto]
DDR2 Channel B REF Voltage [Auto]
DDR2 Controller REF Voltage [DDR2_REF]
SB 1.5V Voltage [Auto]

Important BIOS Functions Conclusion


View All Comments

  • jozeaphe - Sunday, February 17, 2008 - link

    Hi Guys i Just Build a new PC :
    Asus Maximus Formula SE .
    Intel Core 2 Duo E8500 .
    2 GB Ram - 800 MHz ( for the moment ) .

    can any one help to overclock my PC to Max settings within the following :
    1. Stock Intel CPU heatsink\fan ( come with processor ) . No water cooling on the northbridge .

    2. Stock Intel CPU heatsink\fan ( come with processor ) . With water cooling on the northbridge .

    3. The above 2 options but using 2 GB Ram - 1066 ( if thats make a difference ) .

    And Thank u All , .
  • guitronics - Wednesday, February 13, 2008 - link

    I don't know if I have an 'SE',but I have the game Stalker.These Mobo's are NHRA Top Fueler's, not 18 wheeler's. They're Gaming 'Boards,not workstations,or servers.Their cause is overclocking/tweaking. So:Some legacy stuff hadda go...serial and parallel:Buy a PCI card,if you really need it.There are plenty of pci slots.No Esata? There are 6 Sata,and 1 IDE port.2 -GB Lan options.Yes,it does ECC:But why does a gamer want that?There are 1394a ports,not 800 Mhz.Or,at least that speed isn't documented.The USB's time to get on the "dump legacy stuff" wagon.How big a deal is that?Up to 8 GB of memory,and onboard 0,1,5;and 10 Raid support.Put a Blu-Ray on the IDE,run raptors' in raid 0, still have room for > 4 < More drives....Terabyte's, anyone?
    A good case and you can swap 'em big deal."It's a Gaming Machine"!
  • jay401 - Tuesday, November 13, 2007 - link

    I think we've officially reached the point of option saturation, where there are literally TOO many options in the BIOS for most overclockers to ever care about. Sure, it's great for the handful that will actually make use of all of those options, but we're getting dangerously close to the point where it is TMI. Reply
  • RFV - Wednesday, November 21, 2007 - link

    you'd love the DFI BIOS! Reply
  • RFV - Tuesday, November 13, 2007 - link

    I have read that the Asus Maximus Formula SE is now "End Of Line" so you better hurry if you want to purchase one. Asus did the same thing with the Blitz Formula SE, so this is not suprising news, the Maximus Formula SE was always going to be a limited edition board from the get go. Also, fom the reviews I have read on this board from people who upgraded from P35 boards is that the Maximus Formula SE X38 board required more volts than the Asus P5K Deluxe board to reach the same overclock. They also reported that the X38 boards generally ran hotter than the P35 boards at the same overclock. Reply
  • 457R4LDR34DKN07 - Monday, November 12, 2007 - link

    Thanks for the in depth bios descriptions, it has helped me dramatically increase stability while using patriot pc8500 memory. Reply
  • Etern205 - Saturday, November 10, 2007 - link

    What happened to the Maximus Extreme?
  • Raja Gill - Sunday, November 11, 2007 - link

    that's next
  • zoom314 - Saturday, November 10, 2007 - link

    I wonder does Asus still have Locked Multipliers on Extreme cpus still like they do on the P5W DH Deluxe? Meaning any multiplier above the Default Multiplier is locked off to prevent users from overclocking, rendering an Extreme Dual/Quad cpu an Expensive Normal Dual Core or Quad Core cpu(A QX6700 becomes a Q6700 cpu). Of course one can adjust the Multiplier downwards to 6 as Asus say No one needs those upper Multipliers and Hence Asus does Not Support Extreme any cpu!!!! Reply
  • Raja Gill - Saturday, November 10, 2007 - link

    the upwards multipliers work fine on this board...

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