Well, as a last resort, perhaps give the chipset a "no-effort" lo-tec reflow (e.g. a re-heat) on your stovetop.
Prop the motherboard so that it sits about 2 inches (4-6 cm) above one of the burners on your stove, with the chipset positioned right above the burner that you'll use. Doesn't matter if it's an electric or gas stove - both will work OK (except induction type - don't try it on that one.) Make sure all heatsinks are removed, along with the coin cell (CR2032) CMOS battery. Turn stove to low and let the board sit for a few minutes. If you don't have a temperature meter (I don't expect you to), take a fork or a spoon or a knife and moisten it with water. Now put a drop on the motherboard, close to the chipset. If you hear sizzle and the water evaporates, then you know it's gone above 100C. If not, keep heating (might have to increase the stove / burner a notch or two.) Once you get the water to evaporate, keep the board on there for another minute or two, so it goes well above 100C. Then turn off heat and let the board cool off to room temperature (may take 10-15 minutes for that.)
For some of these nVidia chipsets, re-heating to about 150C can sometimes get them going again. So if you're up for some "electronics cookin'", give this a try.
I know there are also a lot of videos showing how to do a reflow in the oven, but I don't like to suggest those, because it tends to make the oven stink like burned electronics for a bit afterwards, and I do use my oven to cook food.