一套来自国外网站的资料，既然是关于电压调整的那么也是维修所关注的，这就可以作为维修参考来利用。这是一套完整的资料，甚至包括了所需的datasheet。（申明：本人对硬件超频不感兴趣。）

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.

Overview
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[attach]3237[/attach]  

This should give you a rough overview of where to find the specific chips, needed for the modifications.
VCORE
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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".



AMD HAMMER VOLTAGE IDENTIFICATION
VID4   VID3   VID2   VID1   VID0   VDAC
1        1        1        1        1        Off
1        1        1        1        0        0.800
1        1        1        0        1        0.825
1        1        1        0        0        0.850
1        1        0        1        1        0.875
1        1        0        1        0        0.900
1        1        0        0        1        0.925
1        1        0        0        0        0.950
1        0        1        1        1        0.975
1        0        1        1        0        1.000
1        0        1        0        1        1.025
1        0        1        0        0        1.050
1        0        0        1        1        1.075
1        0        0        1        0        1.100
1        0        0        0        1        1.125
1        0        0        0        0        1.150
0        1        1        1        1        1.175
0        1        1        1        0        1.200
0        1        1        0        1        1.225
0        1        1        0        0        1.250
0        1        0        1        1        1.275
0        1        0        1        0        1.300
0        1        0        0        1        1.325
0        1        0        0        0        1.350
0        0        1        1        1        1.375
0        0        1        1        0        1.400
0        0        1        0        1        1.425
0        0        1        0        0        1.450
0        0        0        1        1        1.475
0        0        0        1        0        1.500
0        0        0        0        1        1.525
0        0        0        0        0        1.550

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
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VDIMM & VLDT
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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)
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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
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[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
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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.

VChipset & VLDT Measure
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[attach]3247[/attach]

VDroop
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[attach]3248[/attach]

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

1#译文：
介绍
精英NFORCE4-A939是基于nForce4芯片集的主板，可以从Europe购买。虽然价格低廉，从超频选项和主板质量两者来看两者都是真的很好，远超过他的价格。这就使他成为做某些电压调整的最好对象。

所用元件
2x 50K 电位器用于VCore调整
3x ~47K  0805 贴片电阻用于VDroop调整
2x 5位拨动开关用于VID调整
1x 200K 和 1x 10K 电位器用于VDimm调整
1x 500K 和 1x 50K 电位器用于VLDT调整
1x 5K and 1x 500欧电位器用于VChipset调整
调整原则是：电位器的电阻越低电压越高，所以对于第一次和以后的调整，在打开电源之前确认电位器的电阻设置为最大值。

全景图
---------------------------------------------------------------
本图为你寻找特定需要调整的芯片给一个粗略的位置。


2#译文：
--------------------------------------------------------------------
VCORE
--------------------------------------------------------------------
VCore控制器ISL6566资料:
通常VCore的调整有两部分组成。

VCore调整 (part1)
--------------------------------------------------------------------
我们就从几乎最普通的电压调整方法开始，利用控制器的反馈引脚来影响输出电压。这一调整方法需要在pin#9(反馈)和地之间连接电位器。


正如你所看到的，我已经标记了适当的点（pin#9和地）。在作这个调整时，我建议你用两个50K电位器串联后使用，这样你有了一个总电阻100K，但比单个100K电位器提高到2倍精度。现在将电位器连接到图中给出的连接点。减少电阻值就是增大电压。


VCore调整 (part2)
---------------------------------------------------------------
这块主板有一个非常令人头痛的问题：当VCore在BIOS里选择大约"+200mV"（某些情况可能或高或低，按照官方数据资料是 175mV）ISL6566的超电压保护(OVP)就起作用。通常情况下，控制器工作在"VRM9.0"模式，这样对于提供到比CPU核心标准电压高 375mV 就没有问题，现在的问题是他工作在"AMD-HAMMER"模式，而且由于内部OVP触发，所有高于 "+200mV"的选项是无效的。

精英的支持告诉我，由于所说到的问题，在以后的BIOS里高于"+225mV"的项目将被撤消（到目前为止，BIOS最新版为1.1g ）

要解决这个问题只要通过5根所谓"VID-Pins"的针去影响CPU的标准VCore。这些针每个都有一个高于或低于1.2V电压，如果电压高则解释为“1”，如果低则解释为“0”。这些针上的电压是VID码的基础，由“1”和“0”组成了的控制器操作码决定CPU电压的默认值。

我直接标出了5个VID针（黄色字符），上拉电压（绿色字符）以及接地点（蓝色字符）。
正如这些名字所指出的，标为上拉（Pull-Up）就是把VID针上拉为“1”（“高”态），而接地就是拉到“0”（“低”态）。

在ISL6566资料第11页（及以下）或者下表中，你可以找到所要默认CPU电压的VID定义码。由于这个主板的控制器设置为 "AMD-HAMMER"模式，因此你必须依靠这个表！

为进行这一调整，最简单和最好的方法是用2个5位DIP开关并连接每个DIP开关的一边到DIP脚，这就意味着每个5位开关的1#针接到VID0,2#针接到VID1等等。然后分别连接开关的另一行每个针（留下的另一边的一行针）到标有绿色的上拉（PULL-UP)电压。最后另一个开关的剩下的5个针脚接地。现在你可以独立地设定“1”或“0”。当然如果2个开关全部设为Off（不连接），CPU以工厂默认电压启动。

例子：CPU的默认电压为1.4V，按照下面的"AMD-HAMMER"表，编码为"0 0 1 1 0"。

假定我们要增加默认电压到1.55V，为此，我们需要改变 VID1 和 VID2 的默认“1”为“0”，因为1.55V的VID码为"0 0 0 0 0"。实际上我们要做的就是将VID1 和 VID2接地来诱使电源给出1.55V核心电压。
另一个小例子：
要获得默认电压1.1V， VID4 接到PULL-UP电压，VID1 和 VID2接地。
我希望你能懂得这个原理。

警告：VID码只能在主板不通电的情况下改变，并且不要同时把VID针脚连接到地和 PULL-UP电压上 ！


VCore 测量
----------------------------------------------------------------------------------


3#译文：
VDIMM & VLDT
----------------------------------------------------------------------------------
LM324控制器资料：

这个控制器负责Vdimm 和 VLDT。

VDIMM (按照图片，在LM324左边 )
----------------------------------------------------------------------------------
把200K和10K电位器串联为总电阻210K。你也可以用单个200K电位器，但是我喜欢串联使用，单独使用200K电位器不好控制（特别是在电阻较小的地方），有个10K的电位器调节更精密。最后将电位器按图中给出的连接在#3针和#4针(VCC)之间。

VDimm and VTT 测量
-----------------------------------------------------------------------------------


对于VLDT调整我们可以按照调整VDimm一样去做。用一个500K和一个50K 电位器串联，然后把它们焊接到10#和4#针(VCC)之间。要做的就是这些，就象图片中那样。

关于VLDT的重要信息：
VLDT直接和 VChipset相关！这就意味着VLDT永远不会超过VChipset。例如，要有1.5V的VLDT就需要把VChipset设置为1.55V，等等......
你设定的VChipset越高，VLDT的调节范围就越大。

4#译文：
VChipset
------------------------------------------------------------------------------
RT9218 控制器数据资料：


用一个5K电位器和500欧电位器串联，并按图所示把它们连接到12#(FB)和接地脚（3#针）上。

VChipset & VLDT 测量
-------------------------------------------------------------------------------


VDroop
-------------------------------------------------------------------------------

这一调节主要用于调整空闲和加载VCore输出直到获得接近于匹配。即空闲和加载时的电压差别越小越好。
3个Droop电阻用红色圈出，3个电阻相同均为39K（标有393字样）你需要改变为3个相等的较高额定值的电阻。我用3个47K电阻（比原先39K增加20%），我仍旧把它们放好。我的CPU设置为2.6GHz, VCore为1.6V, 结果电压降落为大约 ~0.009V (测得1.648-1.657V)，我认为是相当可以接受的。每个系统性能会有一点儿差别，所以你可以用阻值大一点或小一点的电阻在你的主板上获取最佳效果。

也许我有时间的时候会加一个VTT调整。我在加载的情况下实际测量VTT，看起来似乎没有必要去做这一调整，但是永远无法肯定，也许它对你会有所帮助。

警告：
所有调整的风险均由你自己承担！我不承担上面所说的调整带来的损坏的责任！任何硬件修改绝对会失去保修！请记住着一点。