Introduction The ECS/Elitegroup NFORCE4-A939 is the cheapest nForce4 based motherboard available here in Europe. Although in contrast to the price, the overclocking options and the overall build quality of this board are both really good and far away from appearing cheap. This makes it the perfect victim for some voltmodding action. Required parts • 2x 50K trimmer potentiometers for the VCore-Mod • 3x ~47K SMD 0805 resistors for the VDroop-Mod • 2x 5-position dip-switches for the VID-Mod • 1x 200K and 1x 10K trimmer potentiometers for the VDimm-Mod • 1x 500K and 1x 50K trimmer potentiometers for the VLDT-Mod • 1x 5K and 1x 500R trimmer potentiometers for the VChipset-Mod Adjust all the potentiometers to the maximum resistance. Those are the values to start with - they are very important!
For all mods the rule is: The lower the resistance on those potentiometers, the higher the voltage. So make sure you checked if maximum resistance is set before powering up for the first time after doing the mods.
This should give you a rough overview of where to find the specific chips, needed for the modifications. VCORE ------------------------------------------------------------------------------------------------------------- Datasheet of the ISL6566 VCore-controller:
[attach]3239[/attach]
In general the VCore-Mod consists of two parts.
VCore-Mod (part1) -------------------------------------------------------------------------------------------------------------- Let's start with the nearly common vmod-method of using the controller's feedback-pin to influence the output voltage. This mod requires you to connect a trimmer potentiometer between pin#9(FB) and Ground. [attach]3238[/attach] As you may see, I marked the appropriate points (pin#9 and ground). I advise you to use 2x 50K potentiometers connected in series for this mod. This way you get a total resitance of 100K, but with doubled precision in comparison to a single 100K poti. Now all you have to do is to connect the potentiometers just like shown in the picture. Decreasing resistance now means increasing volts.
VCore-Mod (part2) ----------------------------------------------------------------------------------------------------------------- The board is also suffering from a very annoying problem: The ISL6566's Overvoltage Protection (OVP) activates when a VCore option of about "+200mV" (might be a bit higher or lower in certain cases; official value is 175mV, according to the datasheet) is set in BIOS. Normally the controller should work in "VRM9.0"-mode, thus it should be no problem to supply a VCore of upto 375mV higher than the CPU's standard VCore. The problem now is that it operates in "AMD-HAMMER"-mode and all VCore-options above "+200mV" are quite useless, because the internal OVP gets tripped. The ECS support told me, that due to the described problem, the VCOre-options higher than "+225mV" will be disabled in future BIOS releases (at the moment, BIOS 1.1g is the latest version).
The solution to this problem is simply influencing the CPU's standard VCore, which is generated through the 5 so called "VID-Pins". Those pins either carry a voltage higher than 1.2V or lower than this value. If the voltage is higher, it is interpreted as a logical 1 and if it's lower, it means a logical 0. The different voltages at those pins are the base of the VID-code, which consists of ones and zeros and determines the default voltage of the CPU, according to the operating mode of the voltage controller. [attach]3240[/attach]
I marked the direct connections of the 5 VID-pins (yellow characters), the PULL-UP voltage (green characters) and one Ground point (blue characters). As the name indicates, the pins marked as "Pull-Up" are used to pull the VID-pins up to a logical 1 ("high" status), while Ground is used to pull them down to a logical 0 ("low" status).
On page 11 (and following) of the ISL6566's datasheet, or the html-table below, you find the needed codes to know which pins to influence to get the desired default CPU voltage. The controller is configured to work in "AMD-HAMMER"-mode on this mainboard, so you have to rely on that table! To perform this mod, the simplest and best way is to use 2x 5-position dip-switches and connect one side of either dip-switch to the VID-pins. That means pin number one of either 5-position switch to VID0, pin number 2 of the switch to VID1 and so on. Then connect the complete other row of pins (i.e. all 5 pins that are left on the opposite side) of one 5-position dip-switch to the green-marked PULL-UP voltage and finally the rest of the pins of the other 5-position dip-switch to Ground. Now you can set each VID-pin individually to either 1("high") or 0("low"). Of course, if you leave all the connections on the 2 5-position dip-switches "off" (unconnected), the CPU will still boot with its factory default voltage.
Example: The CPU has a default voltage of 1.4V. According to the "AMD-HAMMER"-table below, this corresponds to "0 0 1 1 0".
Now let's say we want to increase the default voltage to 1.55V. In order to do so, we need to change the "1", that VID1 and VID2 are set to by default, into a "0", because the VID-Code for 1.55V is "0 0 0 0 0". All we have to do in practice is to connect VID1 and VID2 to Ground and bam, we have 1.55V VCore. Another short example: For a default voltage of 1.1V you would need to connect VID4 to the PULL-UP voltage and VID2 to Ground. I hope you understand the principle.
CAUTION: Only change the VID-code using the dipswitches when the system is powered OFF and never connect any VID-pin to Ground and the PULL-UP voltage at the same time!
VCore Measure ------------------------------------------------------------------------------------------------------- VDIMM & VLDT ------------------------------------------------------------------------------------------------------------------------------------------- Datasheet of the LM324 controller:
[attach]3243[/attach]
This controller is responsible for Vdimm as well as VLDT. [attach]3242[/attach]
VDIMM (left side of the LM324 according to the picture) -------------------------------------------------------------------------------------------------------------------------------------------- Connect the 200K and the 10K potentiometers in series, thus getting a total resistance of 210K. You could also only use the single 200K poti, but I like to have a bit more precision using the additional 10K poti to adjust the voltage when the changes are too high using the 200K poti alone (mostly in the lower K-Ohm-range). Finally just make the connection between pin#3 and pin#4(VCC) like shown in the picture.
VDimm and VTT Measure -------------------------------------------------------------------------------------------------------------------------------------------- [attach]3244[/attach]
For the VLDT-mod you do basically the same as for VDimm. You connect 1x 500K and 1x 50K potentiometers in series, and then solder them in between pin#10 and pin#4(VCC). That's all. Just like shown in the picture above.
Important info concerning VLDT: VLDT is directly dependant on VChipset! That means VLDT can never exceed VChipset. For example for a VLDT of 1.5V you would need to set VChipset to at least 1.55V. And so on... The higher you set VChipset, the higher the range of adjustable VLDT voltages. VChipset ------------------------------------------------------------------------------------------------------------ Datasheet of the RT9218 controller:
[attach]3245[/attach]
[attach]3246[/attach]
Take a 5K potentiometer and a 500R potentiometer and connect them in series. Finally connect those potentiometers between pin#12(FB) and Ground/GND(pin#3), just like marked in in the pic.
This mod is used to adjust the VCore output while in idle and load until you (nearly) get a exact match. That means the lower the difference between load and idle volts, the better. The 3 Droop-resistors are marked with RED squares. Those 3 resistors that all have the same value of 39K (marking of "393" on top) need to be exchanged for 3 equal, higher rated resistors. I used three 47K resistors (~20% increase in comparison to the default 39K), because I still had them lying around. With my CPU set to 2.6GHz, at a VCore of 1.6V, I got a Droop of ~0.009V (measured 1.648-1.657V), which I'd consider quite acceptable. Each system behaves a bit different, so you could experiment with higher or lower rated resistors to get the best effect for your individual mainboard.
Perhaps I'll add a VTT-mod if I find the time to. I actually measured VTT under load and it didn't look like it was really necessary to do the mod, but you never know. Perhaps it could help some of you.
Finished! These are all the mods that I discovered for this board. If you have any additional questions or perhaps even some additions to these mod-descritions or ideas about the modifications, then feel free to visit our discussion forums.
Warning: All modifications are done at your own risk! I am not responsible for any damage caused by the modifications described above! Any hardware modification will definitely void your warranty! Keep that in mind. ECS nForce4-A939 Voltmods 译文
