NVIDIA's GeForce GTX 1060 GDDR5X was hailed by many as the AMD Radeon RX 590 killer, but that doesn't seem to be the case after our review. Rather, NVIDIA decided to match performance of the existing GTX 1060 6 GB as closely as possible (GTX 1060 3 GB has fewer shaders). All specs and clocks match the original exactly; the only difference is the use of GDDR5X memory, which is clocked at the same effective frequency.

This looks a bit like a lost opportunity to me since NVIDIA switched to the GP104 GPU. It has more shaders, which would have easily allowed for a bit of an increase in the shader count to make up some ground against the AMD RX 590. Setting higher clocks for both GPU and memory would have provided an additional performance boost as well. The OC potential is there, as our overclocking tests show.

On the other hand, performance matching the GTX 1060 GDDR5 ensures that people know exactly what to expect. The GTX 1060 GDDR5X is just as fast as the Radeon RX 580, and while the recently released RX 590 is around 10% faster, the GTX 1060 does much better in terms of power/heat/noise. NVIDIA's next-fastest SKU, the GTX 1070, is 35% faster. Compared to the GTX 1060 3 GB, the performance uplift is 14% (mostly due to the differing shader count, not due to VRAM size). With these speeds, the GTX 1060 is a good option for full HD 1080p gaming.

KFA2's GTX 1060 GDDR5X OC is a custom design with a 4+1 phase VRM, which should be totally sufficient for this card, especially considering the single 6-pin power input that limits board power to 150 watts anyway. Gaming noise levels are good, and I'd describe the card as "quiet" even though some competing GTX 1060 cards can be significantly quieter. While the card lacks the highly popular idle fan-stop feature, KFA2 picked great fan settings for that state—the card is inaudible during idle unless you put your ear right next to it on an open bench.

Overclocking potential of the GP104 GPU was a bit lower than what we've seen from other GP104-based cards, suggesting that the chips used on the GTX 1060 GDDR5X have been harvested for both defects and clocks. Of course, the defects will be in shading units that are disabled anyway, so this has no effect on the quality of the product or its longevity. Idle power draw of the GDDR5X GTX 1060 is a bit increased due to the bigger GPU, but gaming power is pretty much identical, which is great.

The real highlight of this card is its massive memory overclocking potential. We managed a 44% (!) overclock on memory, which wasn't completely unexpected since the memory chips are rated for a 11 Gbps operation by the manufacturer Micron. Good to see that NVIDIA didn't limit the clocks artificially. Thanks to the large increase in memory clock, the performance of a hand-overclocked GTX 1060 GDDR5X will easily surpass that of a hand-overclocked GDDR5 model. In our testing, the OC'd GTX 1060 Founders Edition reached 76.5 FPS, while the OC'd GDDR5X board reached 82.0 FPS, which is a 7% difference. This means that when overclocked, the GTX 1060 GDDR5X beats the Radeon RX 590, which has very little additional overclocking potential on its own, and thanks to Pascal's power efficiency, the 1060 manages that while using less power and running cooler and quieter.

With a price of around $250, the GTX 1060 GDDR5X comes at the same pricing as the GTX 1060 GDDR5, which is great and just fair considering there is no performance increase out of the box. If you are in the market for a GTX 1060 and can find a GDDR5X model at near identical pricing, then it's worth picking up the GDDR5X variant because it has much better memory overclocking potential, which will yield some extra performance. If you don't plan on overclocking, then both variants can be considered identical, and other factors, like price, should take priority over trying to get GDDR5X memory chips.