In our GTX 980 Ti overclocking endeavors, it was quickly discovered that the card encountered thermal bounds at higher clockrates. Driver failures and device instability were exhibited at frequencies exceeding ~1444MHz, and although a 40% boost in clockrate is admirable, it's not what we wanted. The outcome of our modest overclocking effort was an approximate ~19% performance gain (measured in FPS) for a selection of our benchmark titles, enough to propel the 980 Ti beyond the Titan X in gaming performance. Most games cared more about raw clock speed of the lower CUDA-count 980 Ti than the memory capacity of the TiX.
Further analysis of the data presented that, although the reference cooler keeps the device within safe operating temperatures, it starts to struggle under the thermal load produced by overvolting and overclocking. That's when we reached-out to EVGA to seek sampling of the company's GTX 980 Ti Hybrid ($770), a liquid-cooled version of the GTX 980 Ti. The Hybrid's deployment of traditional air cooling over the VRM and liquid on the GPU should afford higher overclocks within the thermal bounds of the GPU.
This review of EVGA's GTX 980 Ti Hybrid aims to determine the highest overclock possible of the 980 Ti, tests the temperatures and power consumption of the card, and looks at gaming performance.
Previous GTX 980 Ti Content
- GTX 980 Ti SLI Benchmark (2-Way)
- GTX 980 Ti Overclocking Performance a 19% FPS Gain
- NVidia GeForce GTX 980 Ti Review & Benchmark
EVGA GTX 980 Ti Hybrid Specs vs. Reference
|EVGA GTX 980 Ti Hybrid||GTX 980 Ti||GTX Titan X||GTX 780 Ti|
|Texture Filter Rate
|Base Clock (GPU)||1140MHz||1000MHz||1000MHz||875MHz|
|Boost Clock (GPU)||1228MHz||1075MHz||1075MHz||928MHz|
|GDDR5 Memory /
|6GB / 384-bit||6GB / 384-bit||12GB / 384-bit||3GB / 384-bit|
|Memory Bandwidth (GPU)||336.5GB/s||336.5GB/s||336.5GB/s||336GB/s|
First, note that the 980 Ti Hybrid modding kit is available for $100. For users who already own a 980 Ti, the kit can be purchased for boosted performance at a lower cost than the Hybrid standalone.
The 980 Ti Hybrid immediately offers a higher core clock than the reference spec. EVGA's version ships at 1140MHz core, 1228MHz boost, putting it firmly above the 1000MHz / 1075MHz (core/boost) of nVidia's reference design. That's a good thing, but not worth the extra ~$120 price premium on its own.
The most noteworthy change to the 980 Ti is EVGA's improved cooling design. The “Hybrid” portion of EVGA's branding refers to the cooler's fusion of air and liquid cooling for distributed dissipation of heat. A more traditional aluminum heatsink with grilled intake rests toward the front of the card (near the VRM) with a blower fan; the GPU proper hosts the CLC's pump, with braided tubing leading to the 120mm radiator and included fan. A copper coldplate directly contacts the GPU, though we recently highlighted the minimum impact of copper over aluminum for CLC coldplates.
EVGA's CLC is supplied by Asetek and was previously showcased in our CES coverage. Dismantling a Hybrid card, as we did with the 980, showcases a simple design that's primarily liquid cooled.
EVGA's marketing materials suggest an approximate ~52C GPU diode temperature on the 980 ti Hybrid, a marked improvement over the company's ~84C temperature measurement of the reference design. We tested this ourselves with more depth below, but if the gain remotely resembles the materials, overclocking immediately becomes less heat-intensive.
The Basics of Maxwell Overclocking
Overclocking on Maxwell, as we've written in OC guides before, is a little bit different from Kepler and other previous generation GPUs. The basics remain the same as all overclocking: Clockrates are incremented gradually to push GPU core performance, memory clocks can be increased to accelerate memory transactional datarates, and voltage is utilized to stabilize the GPU as the oscillation of the silicon crystals grows more rapid and volatile.
Feeding more voltage to a GPU will stabilize it, but there's only so much room for voltage increases. The GPU has a hard limiter at some manufacturer-defined spec (with nVidia oversight) to reduce the chance of the GPU getting killed from overvolting. In the case of EVGA's GTX 980 Ti Hybrid, the limit seems to be approximately 1.224v; reference voltage hovers around 1.187v pre-OC in our testing.
Voltage increases should be executed lightly, though. They increase heat and can damage the longevity of a GPU with great significance. Silicon likes heat, but only so much, and pushing closer to the TjMax (~91-95C) of the diode will reduce its usable lifespan.
Things change a little bit with Maxwell. We're presented with something called “Power Target (%)” in overclocking utilities, a new option that isn't present for other GPU architectures currently on-market. The power target rests at 100% when untouched, meaning that the GPU will draw 100% of the power it is specified to consume. TDP – defined as the amount of power required to adequately cool and operate the GPU – sits at ~250W for the 980 Ti. Increasing the percentage effectively opens the gates for more power consumption.
Power can be thought of as a limited resource that gets assigned to different functions of the GPU, primarily to the two clocks (core, memory), and is what will throttle overclocking potential when all other factors are stable. The GTX 980 Ti Hybrid can scale to 110% power – adding an additional 10% to base for overclocking. Some other cards, like MSI's GTX 980 (non-Ti), can scale to ~125%. We have not personally seen anything that exceeds ~126% power target.
Maxwell still overclocks the boost clock of the GPU, the GPU vCore, and the memory clock. Power target is used to increase the clockrates. Interestingly, overvolting consumes part of that power target, so there's a balance to be had between overvolting and overclocking to allow the maximum potential clockrate. Voltage and clocks draw from the same power pool.
Continue to Page 2 for the benchmarks and thermals.