Clock Rates, Overclocking & Heat
Manufacturers can claim whatever they want in their marketing material. Actually achievable clock rates are subject to a number of hard-to-control variables, though. GPU quality, for instance, plays a big role, and there's no way to pre-screen what you get on that front. So, it's absolutely possible that a nominally slower card made by one board partner ends up faster than a more aggressively-tuned model from another partner. As a result, comparisons between products have to be approached with an understanding of some inherent uncertainty.
Board vendors can, however, control the settings and environmental factors that affect how GPU Boost ultimately determines operating frequency, depending on the situations it encounters. Beyond specifications like the power target or clock offset, temperature under load is perhaps the most influential factor in defining sustainable performance.
For the EVGA GeForce GTX 1080 Ti FTW3 Gaming, we measured an initial GPU Boost frequency as high as 1974 MHz during our gaming loop. As the card warmed up, it maintained an average of ~1860 MHz during our 30-minute measurement.
During our stress test, the power limit's constraints are more palpable, manifesting as lower clock rates and, consequently, lower temperatures.
Of course, the card does tolerate some additional overclocking. In our case, we achieved a stable 1974 MHz under air cooling, with peaks as high as 2037 MHz. To achieve 2 GHz+, we had to set EVGA's fan control to 100%, causing the card to run much noisier than its stock configuration.
If you plan to overclock, consider increasing the power target to its maximum, or at least to 120%.
The table below contains results after configuring our card in Afterburner and a long test run in The Witcher 3.
|Clock Rate Increase||Power Target (Afterburner)||Voltage (Afterburner)||Avg. Boost Clock||Avg. Voltage||Power Consumption|
|No||100%||Standard||1860 MHz||1.030 V||286.2W|
|No||100%||Maximum||1885 MHz||1.043 V||289.4W|
|No||120%||Standard||1974 MHz||1.050 V||320.7W|
|+25 MHz||127%||Maximum +Fans @ 100%||2037 MHz||1.062 V||331.1W|
Getting a good overclock from your memory requires perseverance and a bit of luck. Seemingly stable settings might work short-term, and then prove dicey after a few hours of gaming. In the case of our sample, an extra 350 to 400 MT/s was feasible. Beyond that, performance started sliding the other direction.
Because the backplate plays an active role in cooling, it has to stay on for our measurements. We did lay a bit of harrowing groundwork, though. Before taking our readings, we removed the backplate and identified the card's hot-spots. This gave us the information we needed to drill holes into the plate, directly above those areas. These holes allow us to take precise measurements, even with the plate attached. Just bear in mind that our numbers don't correspond to EVGA's thermal sensors. Because we're looking at thermal load directly under the relevant components, certain deviations are unavoidable.
Reading from the GPU diode, we observe 71 to 72°C on an open test bench, while the PCB underneath remains right between those two values at 71.4°C. The other temperatures are wholly acceptable at this point.
In a closed case, the GPU's temperature rises to 75°C. Meanwhile, the GPU package hits just under 78°C. This is already three Kelvin more, indicating that the backplate is already nearing its cooling capacity limit. Nevertheless, EVGA's voltage regulation circuitry and memory modules continue operating at a comfortable level. The GDDR5X is rated for temperatures as high as 95°C, after all.
During our stress test, the card runs even cooler since the GPU's power target limits clock rates, driving voltage down and limiting thermal output. Only the memory heats up a bit more.
But this card gets hotter still; during our stress test in a closed case, the difference between GP102 and its package reaches four Kelvin.
As the card cools down, the infrared image reverses and it's easy to see where the cooler draws heat away most effectively (namely, below the GPU package).
All in all, the GeForce GTX 1080 Ti FTW3 Gaming's thermal solution is sufficient, and if we keep in mind that this is a dual-slot card, you might even say it's pretty darned good. It's hard to imagine a more effective implementation, given the physical constraints EVGA's team was under in designing a heat sink able to go up against the 2.5-slot competition.
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