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How-To: Gainward 7600GS PCI-e Voltage Mod
Graphics Cards
Written by phatic   
Friday, 01 September 2006 18:43
Article Index
How-To: Gainward 7600GS PCI-e Voltage Mod
Voltage Mod
Voltage Mod (Cont.)
Voltage Mod (Wrap up)
Cooling Mod
Vantec Mod
All Pages
If you own a Gainward 7600GS, and would like to squeeze some extra performance out of this mid-range card, then look no further. This article will show you everything needed to achieve some very impressive clock speeds, for quite a small cost.

Basically, this involves soldering two potentiometers (variable resistors) onto the card, which allows the GPU and memory voltages to be adjusted. This will allow much higher clock speeds to be attained. But, since more volts = more heat, a cooling upgrade is required to get the most out of this mod, as heat will quickly become a limitation. This article will therefore also include a DIY cooling mod, that costs about 1/4 of the price of a new VGA cooler.

Disclaimer: All of the following is done at your own risk, and will void your manufacturer's warranty. Please read through the whole article before starting.

Firstly, here's a list of all the necessary materials.

Voltage mod

  • A 25-30w Soldering Iron
  • Some 60/40 Solder
  • A Multimeter
  • 2 x 25k ohm potentiometers
  • Some fairly thin wire
  • 2 x SMD grabbers (optional)

If you really have an aversion to soldering near tiny components, the SMD grabbers can be used. These will save you from the most difficult soldering. Otherwise, if you've got some old computer parts lying around, just practice on these, and you will be fine.

Cooling mod

  • A drill
  • Some cable ties, or strong wire
  • Pair of pliers
  • 92mm fan
  • A 15-20k ohm potentiometer (optional)

The best choice for a fan would be the Vantec Thermoflow, because it comes with an in-built thermistor, which can be replaced with a potentiometer for a simple fan speed controller. If you don't want the fan controller, any 92mm fan will be ok.

Voltage Mod

The two potentiometers are for the GPU core voltage (vGPU) and memory voltage (vMEM). By attaching these to the voltage feedback pins on the voltage regulator chips, you can quite simply reduce the resistance to increase the voltage.

Navigate to the following section on the top of your graphics card.

(Click for larger image)

Firstly, measure your stock voltages. Since you must do this with the computer turned on, be careful. So, set the multimeter to 20v DC, and touch the red probe to one of the points below, and the black probe to ground (the graphics card mounting bracket is a good ground spot).

(Click for larger image)

vGPU should be 1.15v, and vMEM should be 1.9v. In the future, use these points to measure the voltages once they have been altered.

Next, measure the resistance between the following points and ground. This is done with a multimeter set to 20k ohms, and computer turned OFF. These are the feedback pins of the voltage regulator chips - rGPU is on the GPU voltage regulator, and rMEM is on the memory voltage regulator.

(Click for larger image)

rGPU should be around 1.39k ohms, and rMEM should be around 1.29k ohms.

Now comes the soldering. You will need to attach the potentiometers between these pins and ground. If you bought the SMD grabbers, just clip them onto the pins (if the pincers are too big, file them down a bit). Otherwise, you'll need to solder some wire onto the pins, and the potentiometers onto the wire. Here's a visual guide. I've also suggested some ground points which can be used.

(Click for larger image)

If your potentiometer has three pins, use a multimeter to make sure you're using the right ones before soldering them. Set it to 200k ohms, and measure the resistance across two of the pins by touching the red probe to one pin and the black probe to another. Make sure the potentiometer is turned fully in one direction, and you should get a reading of 25k ohms. This will confirm that you have the right pins.

Once it's done, it should look something like this.

(Click for larger image)

Now, with the potentiometers set to full resistance, measure the resistance between the two pins you are using. The resistances should be fairly close to those stock values (1.29k ohms for memory and 1.39k ohms for GPU), or most likely a little lower. To predict the new voltages before powering up, use this formula:

v(new) = v(stock) x [ r(stock) / r(new) ]

So, for example, if your new resistance for GPU core is 1.3k ohms, 1.15 x (1.39 / 1.3) = 1.23v.

Now a final few words of advice. Take things slowly, increasing the voltages one at a time. I'd suggest taking the core as far as it will go first. Once the high temps induce artifacting, knock back the voltage a little, so that the load temp drops a few degrees. rthdribl or ATITool's artifact tester will put your GPU under max load, and find the top temp it will reach.

You may have to knock back the memory clock speeds a bit once the core clocks get really high. I had to drop the memory from 470Mhz back to 450Mhz once the core went over 600Mhz, otherwise it artifacted very badly. This was a fair trade-off, since the max core speed reached was 750Mhz.

Also, the Memory is rated up to 2.3v maximum - anything over this may cause permanent damage, so stay below this. The memory on mine became less stable above 2.15v anyway, so this is fine.

Cooling Mod

This one is fairly simple. Just attach the 92mm fan to the stock heatsink, by drilling a few holes, and securing it with some strong wire. This also provides a nice place to mount the potentiometers. Also included is the thermistor -> fan controller mod.  After this fan mod, load temps dropped by around 10 degrees celcius.

Firstly, drill four holes in the heatsink where marked. Removing the heatsink from the card would make this job much easier.

(Click for larger image)

Now just thread the wire through the holes in the heatsink, and the holes in the fan. Just make sure the fan is pointing in the right direction before you tighten it with some pliers.

(Click for larger image)

Well, that wasn't too hard! If you want to mount the potentiometers on the side of the fan, just use some double sided tape, or blu-tack might even work.

(Click for larger image)

If you've bought the Vantec Thermoflow, here's how to substitute the thermistor for a potentiometer, thus creating a fan controller.

Firstly, break off some of the plastic covering the fan PCB, above where the thermistor is attached. I haven't got any pics here, but it's a small green thing sticking out the side of the central part of the fan. It's hard to miss.

Just chop off its' legs. If you dont want to break the plastic fan covering, you may be able to solder the wires onto what remains of its legs, but this didn't work for me, so I soldered the wires onto the joints that it was attached to. They're a bit hard to see in this pic, but very easy to find - just look for the spots where the two ends of the thermistor are attached to the PCB.

(Click for larger image)

Solder on the two wires like so, and attach the other ends to the potentiometer. You can then adjust the potentiometer to alter the fan speed.

(Click for larger image)

And now for the results!

Stock Ratings

vGPU: 1.15v
vMEM: 1.9v
Core Speed: 450Mhz
Memory Speed: 800Mhz
Load Temp: 48°
Cooling: Stock Heatsink
3dMark03: 9200

After Vmod

vGPU: 1.75v
vMEM: 2.15v
Core Speed: 750Mhz
Memory Speed: 900Mhz
Load Temp: 66°
Cooling: 92mm fan attached to stock heatsink
3dMark03: 10950

Well, that's pretty much it. Good luck, have fun, and enjoy that extra performance!

Credits: Many thanks go to yantronic from VR-Zone for helping me with the vmod!

[Ed: Forum discussion thread is here ]

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