http://www.guru3d.com/news-story/middle-earth-shadow-of-mordor-geforce-gtx-970-vram-stress-test.html
Here we go. They went past 3.5gb and could not find stuttering.
I bet I could find benchmarks where the 290x starts to crap out once the settings are turned up high enough.
Storm in a teacup.
Ugh, that Guru3D is about the worst example you can pull up right now, see these posts:
http://hardforum.com/showpost.php?p=1041390866&postcount=319
http://hardforum.com/showpost.php?p=1041391037&postcount=329
http://hardforum.com/showpost.php?p=1041391044&postcount=331
And of course then you have sites showing the following:
Source
Google Translate of the last two paragraphs:
However, once the memory above 3.5 gigabytes is really needed and the driver can not shirk that it be situated in Ultra-HD with 4 x MSAA and "High" texture maps with up to 3,980 MiB, shows that there must be tricked, to view the full four gigabytes. The frametimes be far more uneven compared to the GTX 980 (which, incidentally, may approve about 70 MiB more still) and it shows not only in the diagram, but sensitive natures can do this in a direct comparison in the game notice. The Radeon, according to a shaky performance in Full HD, here acts over long distances at the level of (clocked down) GTX 980, but gets to the end of our benchmarks towards problems of memory management.
Away from "normal" benchmarks are the differences between GTX 970 and 980 clearly than would imply the previously known specifications - at least in the on our benchmarks. While the behavior of the driver and the heuristic possibly obtain different application-specific good results, remains a stale aftertaste whether one or the other or stuttering stutterers in the border area with the previously announced Nvidia configuration would not be avoided.
Same thing seen with other games like ACU, Far Cry 4, and Talos Principle. You can check their frame time results here
As an aside, interesting how most of the US based sites have either kept silent or announced everything is peachy, but those Germans keep finding problems. Those pesky Germans I tell ya!