this is my first post here. I think I have finally found a forum, where fellow enthusiasts like to share thoughts and information. I'm new to voltmodding GPUs, but I am quite experienced in electronics. There is a lot which I don't know, but only little I can't learn. I may be wrong in my arguments and wish to be corrected! This is how I learn =)
I have a rather good Palit GTX 670 Jetstream. It runs 1350MHz core 24/7 with just the modified bios. I do have watercooling (check out my rig!). The card still runs very low temps, so.. hunger grows as I eat =)
I have not found any completed voltage mods for GTX 670. Now I do mean reference PCB models.. This feels odd considering the popularity of this card! I've read about TIN's GTX 680 mods. Also I've checked out many other mods. I find it displeasing how in many cases the thought is not delivered 100%. Only the wiring...
Well, about TIN's method. In his article he hardwires VID pins. This way bios cannot control the voltage at all. Although my GTX 670 uses a different PWM circuit (NCP5392), I found the VID pins follow the same standards. Same amount of pins and same combos give same results in Vout. I'm sure the two most significant VID pins are hardwired just like in 680. Also the unlocked bios voltage range speaks in favor of my argument. If MSB is tied to 0 and second MSB is tied to 1, the voltage range is 0.81875 V - 1.2125 V. Therefore I'm quite sure this method is available for GTX 670! This is not a very nice way, because you have zero control via bios. The card will have a solid voltage. The bios cannot change the voltage by load. Also this method requires cutting of many traces and a lot of soldering. The card could never be restored. Warranty is lost when I put the waterblock on, but still I prefer to do stuff so that I may undo it later =)
Another way could be to alter the feedback. This way you could slide the voltage region higher. Bios would think it's changing the voltage inside 0.82-1.21V, while the voltage region truly was a tad higher instead. This is the mod I'd feel comfortable with. Now then.. Which contact to alter?
The PWM chip of GTX 470 is a close relative to 670's. I've looked at some 470 mods. This one seems to connect VR (100ohm) between VS+ and VS-. I totally get this! Core voltage is connected to VS+ pin, while core GND is at VS-. You pull down the feedback input (VS+) to lower the feedback voltage. This requires there to be notable resistance between VS+ and the actual core voltage. If the contact is low impedance, the VR won't do much.
Another signal I thought about pulling down is the VFB signal. I'm not sure about this because there are other circuits it might mess up..
I put some serious thought into this, hope you guys read
I appreciate all feedback and help!