Fallout 4 was Bethesda's first 64 bit game. When Beth bought out the Fallout franchise they used the game engine they had from Oblivion to make Fallout 3, giving it a few updates and tweaks. Then they took the Fallout 3 game engine and used it to make Skyrim, again, giving it tweaks. They have been using the same game engine since Morrowind in fact.
But I think they actually made a brand new game engine with Fallout 4. It is 64-bit, so it must be all new code. Unless there is still some 32-bit code buried in there (which would not surprise me, knowing Bethesda), but I have not seen anyone say so. Given their history of reusing the same game engine over and over, they undoubtedly used the Fallout 4 game engine to make the Skyrim SE (since it is also 64-bit). When their next Elder Scrolls or Fallout game comes out they will surely use the same engine again, with more tweaks. So future Beth games will all be 64 bit.
Really though it is about time. We have had 64-bit operating systems for what, 15 years now? When Windows 95 came out we were getting true 32-bit games within just a few years.
TBH, one thing I don't like about Skyrim's graphics is how dark and grey it is when it is snowing. When I go out when it is snowing the sky is all grey to be certain, but the air is bright, because snow is white, and reflects light. All the other colors in the world don't become muted either.
This woman's scarf would be grey or black in SkyrimThis post has been edited by SubRosa: Nov 2 2016, 04:19 PM