Being a “bencher”, I like to push my computer hardware to the limits and beyond. Nice new six core Intel core i7 Extreme 980x cpu runs at 3.3ghz stock? That’s all well and good, but I’d rather run it somewhat over five gigahertz, and compete with plenty of other people in how high I can get the cpu to run. Some of the benchmarks involve calculating Pi to one million or 32 million digits, or calculating a few million (or billion) square roots.
In the video card end of things, the benchmarks involve rendering specific scenes either as fast as possible, or with the largest number of frames per second possible. The higher you can overclock, the more frames you can render and the higher your score will be. Overclocking to the extreme limit requires very good cooling, and rather more voltage then the manufacturers want you putting through the cards, that means it’s time to bust out the soldering iron and have some fun! Hit Read More for more!
The Precautions
The downside of this hobby/job/addiction is that it’s rather hazardous to the hardware involved, the 980x cpu mentioned above is now rather dead. Because of that, benchers tend to benchmark plenty of old hardware as well. If a $20 video card dies it’s unfortunate, but doesn’t sting quite as much as a new $500 GTX580 would! These old parts don’t get me anywhere in the overall rankings of overclockers, but they’re good practice and fun to benchmark.
On the practice front we come to the subject matter of todays article! If you want to score way up at the top you are pretty much forced to take out a soldering iron and start soldering wires and variable resistors and such to your nice new $500 video card. This naturally voids the warranty (overclocking itself may or may not void the warranty, depending on the company), so one slip of the soldering iron and it’s bye bye $500 card! Hence, it’s a good idea to practice soldering on cheap hardware before tackling larger projects.
In my case a friend of mine on my benchmarking team gave me an old GeForce 6800 video card for free, he didn’t need it anymore and figured I could have some fun with it.
I took the heatsink off the card and studied it to find the “voltage controller”, the chip that controls how much voltage is given to the video card processor and it’s ram. More voltage almost always allows the part to overclock further, but comes at the price of more heat and a shorter life.
Once I found the controller I was able to find a datasheet for it. A datasheet is a document written by the manufacturer of the chip that details how it works, how to set voltages, it’s size, requirements, and so on. Using that datasheet I was able to find the two “feedback” pins, which are how the voltage controller reads the voltage being applied to the core and ram. At that point it can look at the voltage and check it against how much it knows it is supposed to give the core or ram, and adjust up or down as needed.
Let the Voltmod begin
To “voltmod” the card, I attach some variable resistors to those feedback pins, using the variable resistors I can shuffle some of the voltage away from the controller so it can’t see it. In this case the normal voltage for the video card core is 1.3 volts, that isn’t nearly enough for what I want to do so I set the resistor to make .35 volts of that disappear. Now the controller thinks it is only giving the core 0.95 volts, and raises the voltage until it looks like 1.3v again. Now of course it is really 1.65 volts! At this point I can overclock much further and get higher scores. The same goes for the ram, identical process.
By this time there is absolutely no way that the stock cooler can handle the heatload, so I attached a far larger cooler to the card, and put heatsinks on each individual ram chip as well, as they get rather hot without it.
Using this voltmod I was able to overclock the card from it’s normal clocks of 350mhz core and 300mhz ram to 535mhz core and 450mhz ram, far higher than the original core speed! Between the core and the ram the card is over twice as fast, and I managed to get the highest score on HWBot in Futuremark’s 3dmark03 benchmark!
By this point you can likely guess what the parts in the picture are, but if not here you go:
The blue boxes are the variable resistors, they are connected to wires that are soldered to the core and ram feedback pins on the voltage controller. They are then soldered to safety resistors and then to ground. Without those resistors it would not be hard to accidentally give the core or ram 12 volts and blow it to bits!
The hard drive connector at the top is wired to ground and core and memory output voltages so that I can check them easily with a multimeter.
Next up I’ll be doing this to a couple $50ish cards for a couple guys on the benchmarking team I’m part of.
WARNING: VOLTMODDING CAN DAMAGE YOUR HARDWARE. ANY VOLTMODDING IS DONE AT YOUR OWN RISK. FUNKY KIT IS NOT RESPONSIBLE FOR ANY DAMAGES CAUSED.
