Temperature in a Closed Case
This heat sink's fin alignment is optimized for vertical operation, and it benefits from cases with some airflow. My idea here was to go completely noiseless. I wanted to test a true passive solution. So, we're once again using our Enermax Fulmo ST, testing in a closed case.
It takes just 20 minutes for the Maxwell-based GM107 to hit an 80 °C ceiling. Then, the chip gets some help from Nvidia's GPU Boost technology and its ability to back off clock rate to duck under certain power and thermal situations. Even the voltage regulators continue working within their specifications. Their roughly 93 degrees after an hour of work still falls within the safe zone.
Clock Rate And Throttling
Nvidia might not have been considering passive operation when it designed this card, but what we see from it (including GPU Boost performance) is still impressive.
What follows is a 40-minute loop of Metro: Last Light. Boost clocks do drop, but they also stabilize after the card hits its thermal target zone.
In the end, GPU Boost to around 1136 MHz, though as a percentage, performance drops more noticeably. Remember, the actively-cooled card reached a GPU Boost clock rate of 1162 MHz, occasionally dropping to 1150 MHz.
The base frequency of these cards doesn't change. You're guaranteed at least 1020 MHz, regardless of your cooling solution.
Our passively-cooled GeForce GTX 750 Ti loses about two percent of its performance compared to the reference model. To better hammer that point home, the aggressively cooled and factory-overclocked Gigabyte GTX 750 Ti Windforce OC achieved 1.3 percent-higher performance than the reference card. In the end, we're talking about about a three-percent performance loss in the quest for passive cooling.
This is for Cautious People
If you're not willing to trust Nvidia's 80 °C temperature target (the company says 95 degrees is the GPU's thermal threshold), you can of course set a lower target of, say, 70 °C. That's going to give up a lot of performance though, and we're not sure such a compromise makes sense. At that point, you might as well buy a Radeon R7 250, which you don't have to build yourself. They already ship passively-cooled.