Anyone who flashes there Bios and is unable to Re-Flash card before sending in for warranty can have claim denied. Nvidia can also deny cards they suspect of overvolting due to degeradiation of transistors from electromigration. Giving more voltage than 1.175v will void the warranty. The limit on max voltage is very simply to prevent damage to the GPU chips. Runnig oner 1.175 over time will damge cards.Here is the official NVIDIA response to Overvolting:
Some of our best and most passionate customers have told us (though forums, partners and directly) that they are frustrated with our position on GPU Overvoltaging. So we feel that it is important to explain exactly what our position is and why we feel that it is important.
We love to see our chips run faster and we understand that our customers want to squeeze as much performance as possible out of their GPUs. However there is a physical limit to the amount of voltage that can be applied to a GPU before the silicon begins to degrade through electromigration (http://en.wikipedia.org/wiki/Electromigration
). Essentially, excessive voltages on transistors can over time "evaporate" the metal in a key spot destroying or degrading the performance of the chip. Unfortunately, since the process happens over time it's not always immediately obvious when it's happening. Overvoltaging above our max spec does exactly this. It raises the operating voltage beyond our rated max and can erode the GPU silicon over time.
In contrast, GPU Boost always keeps the voltage below our max spec, even as it is raising and lowering the voltage dynamically. That way you get great performance and a guaranteed lifetime.
So our policy is pretty simple:
1. We encourage users to go have fun with our GPUs. They are completely guaranteed and will perform great within the predefined limits.
2. We also recommend that our board partners don’t build in mechanisms that raise voltages beyond our max spec. We set it as high as possible within long term reliability limits.
3. The reason we have a limit on max voltage is very simply to prevent damage to the GPU chips. At NVIDIA we know that our customers want to push their GPUs to the limit. We are all for it, and as a matter of fact NVIDIA has always prioritized support for hardware enthusiasts by providing tools to access hardware settings and by supporting our board partners in creating overclocked enthusiast products. Leading up to the GeForce GTX 680 release for example, we worked closely with developers of 3rd party overclocking utilities to make sure they fully supported GeForce GTX 680 and GPU Boost on the day of launch.