Modding the PC-DL

Vdimm Mod

This is one of the most crucial mods that you can do for the PC-DL.  At stock settings, the PC-DL supplies 2.49 - 2.5 volts to the memory.  This is just simply not enough to push the 200 FSB operation window.  We need to modify the circuit containing the  RichTek RT9202 chip so that we can apply no less than 2.5-3.0 volts (+/-).

Note:  This mod requires slight soldering skills, proceed with caution!  If you feel it is not necessary to void any motherboard or ram warranties, please visit the PC-DL User Site for the solderless method.

Things you will need:

• Multimeter
• Any Variable Resistor greater than 1k ohm, also known as potentiometer, or "pot" for short
• Few inches of wire
• Soldering Iron with a pencil tip
• Solder ( Rosin Core Solder )
• Steady hands

Figure 1.1 - Supplies

The RT9202 IC has an FB pin - the feedback pin.  The IC measures voltage at the FB in order to adjust the output voltages and duty cycles to the MOSFETs powering the DIMM modules.  As you can see in Figure 1.2 below, the FB pin is pin 6.  Note that pin 1 of an IC is always to the left of a notch or dot.

Figure 1.2 - Identifying the "Bump" on the RT9202

Figure 1.3 - Chip Identification

Note:  The leg marked in yellow is the FB pin #6, and the small yellow circle shows where the "Bump" is located

Now, familiarize yourself with the area between the DIMM slots and the sideways ATA connector.  The image below shows the various parts involved in this mod.  First, the square is the RT9202 IC.  Second, the circle is the 2nd pin of an unpopulated jumper which, lucky for us, is directly tied to the FB pin of the RT9202.  You can verify this yourself by performing a continuity check with your voltmeter.  Lastly, the triangle below shows an unpopulated capacitor's ground pin.  Click on the image below for a full-size pic.

Next, connect the MIDDLE LEG of your variable resistor, also known as the wiper leg, to the pin shown in the circle above.  Finally, connect one of the other legs of your variable resistor (does not matter which one) to ground.  The unused ground in the triangle above is a good choice. 

The image below shows what you may get.  The yellow box with a small screw on top is a trimmer variable resistor with one of its legs directly soldered into that ground pin beneath it.  It is also glue-gunned to the board for stability.  As you can see, there is a red wire from the variable resistor to the jumper.  Click on the image below for a full-size pic.

Detailed photo of a 100K ohm trimmer pot:

CPU Socket Mod

The next step in achieving 200MHz FSB and DDR400 memory timings is fooling the BIOS that you have a Nocona CPU.  This is easily accomplished by doing THREE things:

• Bridge AA2 and AA3

• Insulate AB3 on your CPUs

• Set the jumpers correctly on the MB for 200MHz FSB

First, we need to bridge AA2 to AA3.  This can easily be accomplished by putting a very fine conductor in the CPU socket.  This method is also known as the "u-wire" mod, because of the shape that the wire takes when bent and inserted into the socket.

Below is an audio cable no longer being used.  Its shield is comprised of many strands of fine silver wire which is perfect for this mod.

Simply snip off a few strands, about an inch long.  Then, bend it into a u-shape as shown below.  Now all you have to do is locate AA2 and AA3 sockets, and simple drop the u-wire in there!

The image below shows the pin mapping of the CPU socket.  Pins AA2 and AA3 are shown in the blue circle below. 

Insulating AB3 can be done by using the insulator of a very small-gauge wire and putting it around pin AB3 of your CPU.  Use the image above to locate AB3.  Keep in mind that the image above is that of the socket, and the mapping of the CPU pins will be a mirror image.  AB3 is close to the lower left "empty-pin" corner of the socket.

Below is a pic of a pair of Xeons next to some Kynar wire.  Kynar wire is a 30AWG solid wire with plastic insulation.

A pushpin can be used to enlarge the insulation opening for easier insertion over the AB3 pin.  The CPU in the background below already has the insulation on AB3.  Again, note that the red insulator is close to the lower right "empty-pin" corner of the CPU - mirror image of the socket above.

For those of you that prefer not to insulate AB3, you can always break it off.  Doing so voids your warranty.

200 MHz FSB Results

Here are some screenshots documenting the success of these mods, with 1:1 DDR400 as well.

Using ClockGen, we were able to push the PC-DL Deluxe to 250MHz FSB!  Yes, that's 1GHz QDR!

Other PC-DL users have reached higher FSBs without any sort of unwieldy cooling mechanisms.  The only requirements were higher DIMM voltages and solid memory modules that can handle the higher FSBs.

At this point, no other dual-Xeon motherboard has ever achieved an FSB of 250MHz or faster with both CPUs installed.  Amazing performance!