General Instructions and Disclaimer
There are many revision of the Intel "Bad Axe" is circulation. These mods have been successfully tested on a rev 302 board. This isn't intended to imply that earlier revision boards cannot be modified, simply that I can't guarantee this. Standard disclaimers apply, neither myself nor Xtremesystems.org is resonsible for any damages to ANY of your hardware as a result of these modifications. These instructions are provided "as is" with no warranty either expressed or implied. With that being said, have fun.
Note: There is nothing terribly difficult about completing this mod but based on size of the components that need to be added I would rate this mod at an "expert solderer" level. If you feel at all uncomfortable doing this I would highly recommend that you have the actual changes done by someone better qualified or don't do this at all.
Now, onto the good stuff. With the following modifications your Intel D975XBX board will be "Conroe" Core 2 Duo/Extreme ready. Backwards compatability is maintained.
BIOS required: 0618 (February 2006) or later. Avoid BIOS 1009....it is broken. I recommend 0908 or 1304. My experience with 1073 was not good. Best practices, flash to the BIOS before you make any of the following hard changes to the board.
Image 1. Conroe Support - four (4) modifications (of 5 total).
Step 1, 2 and 3 - solder in each open pads shown the following:
SMD 0402 1.0 kohm resistor (I recommend a tolerance of 5% or better). Note: 1.0 kohm = 1000 ohms, be careful.
Step 4 - solder in the open pad shown the following:
SMD 0402 24.9 ohm resistor (I recommend a tolerance of 1% or better).
Image 2. Conroe Support - one (1) modification (of 5 total).
Step 5 - solder in the open pad shown the following:
SMD 0603 0 ohm resistor or simply solder between the pads to short them together.
Image 3. Vcore "Modification" - unlocked BIOS for ALL chips (optional)
Notice the 3-pin header called "BIOS CONFIG" used for flashing and maintenance mode. Now...notice the empty silk-screen locations (OC DEBUG) above that in the picture? Intel has purposefully not shown the through-holes in their pictures as they have been blacked out. (I have shown them with the yellow circles.)
Mod: Short together the holes shown. Use either conductive ink or solder. If you wish, install a header and use an extra shorting bar from your included accessories to make this mod changable!
When you boot and enter the BIOS you will have full control over CPU VID (vcore), Enhanced Power Slope (reduces vdroop to 50% default), and Default Bus Override (533, 800, 1066, 1333Mhz) with the ability to go 30% over your set FSB! ClockGen also works with the ICS 954123 PLL chip. Please donate if you find the program useful.
Note: Some people have reported that this mod is not needed with B0 stepping Conroe ES CPUs on the newer rev 304 MB. Do the mod if you need to, otherwise this gains nothing.
Image 4. Vddr Modification - up to ~2.8V for your DDR2 (optional)
A special thanks to TAM, PRTeamJapan and all the members of Team Japan for their work in creating this modification!!!
Mod: Connect a 10K ohm potentiometer from Pin #1 of U6H1 (SC2612E) to GND. Set to maximum resistance before connecting. Lower resistance to raise volts. It is recommended that a separate 220ohm resistor be added to the VR in series to prevent grounding Pin #1. This allow for ~2.8V to your DDR2. Make sure you know what your memory can handle before you put excessive voltage to it!
Note: This mod can be done on the newer rev. 304 board also!
Image 5. Extreme Vcore Modification (not recommended for those not using LN2)
A special thanks to TAM and all the members of Team Japan for their work in creating this modification!!!
Complete Image 3. Vcore "Modification" - unlocked BIOS for ALL chips before making this modification. That step allows selection of 1.6v by BIOS (~1.565v real) for the CPU. This is more than enought to carry most users to maximum clock with their Conroe CPU. If you have more exotic cooling (read: LN2) then complete this modification and the one below, if desired, to allow for manual temperature offset.
Mod: Connect a 50K ohm potentiometer (set at maximum resistance) rrom Pin #4 (red points) of ADP3189 to GND. Lower resistance to increase Vcore. This allows for ~0.2v increase over BIOS values (~1.75v real) at 6K ohm. Lower settings cause a shutdown on voltage protection (a modification is being worked to get around this). The green dot shows the measure point (to ground) for Vcore.
Note: This mod can be done on the newer rev. 304 board also!
Image 6. Tcore Modification (not recommended for those not using LN2 or other cooling > -127C)
A special thanks to OMEGA and all the members of Team Japan for their work in creating this modification!!!
The onboard thermal diode is monitored by the SMSC EMC6D103CZC and allows reading temperatures as low as -127C (1/2 of an unsigned 8-bit boundry). This modification allows for a manual positive offset.
Mod: Remove the resistor from the pad shown below and solder a 200 ohm potentiometer in place. Set to 100 ohms for ~30C increase. More resistance creates a bigger positive thermal reading offset. Do not set too high or you may run into problems with water or air cooling (remember to set back when you don't need the offset).
Allowing the thermal diode to go below -127C will cause the board to alarm and shutdown on thermal protection. This allows LN2/cascade users to go MUCH lower. (Using bigger VRs may allow for an even bigger maximum tunable offset.)
Note: This mod can be done on the newer rev. 304 board also! Notice that you can see some of the SMT resistors soldered to a rev. 302 board in this pic. (The components soldered in place are even bigger than those called out in the guide steps 1-3 above!)
Last note: Contact me (via PM) if you would like me to supply you with the required components to complete the "Conroe support" mods. I have them ready to go and can deliver anywhere in the world. Just put "D975XBX Mod Parts" as the PM title.