The card codenamed “GTX 1070 AMP Extreme Core GDDR5X” today appeared on ZOTAC website, but it was quickly removed (though, you can still access it through Google Cache).
This model features GP104 GPU with 1920 CUDA cores, but also 8GB of GDDR5X memory clocked at 8 GHz. So far the faster variant of G5 memory was only reserved for GTX 1080 series, and also recently for GTX 1060 G5X edition.
It is believed that NVIDIA is trying to get rid of G5X chips before mass producing G6 for mid-range models, such as upcoming GeForce RTX 2060.
So GTX 1060 GDDR5x and now GTX 1070 GDDR5X on top of the GTX 1080 with GDDR5X instead of GTX 1070 Ti with GDDR5
However, the listing has since reappeared, only this time it shows the usual GDDR5 memory, not GDDR5X. I asked Zotac what was up with that, and the company confirmed it was just a typo."It will only support the normal GDDR5 [memory]," Zotac said.