EDIT: Changed format and some content of post after double checking and expanding results
Using a Windows Surface Book (1st gen) with Enhanced performance. Disabled all mods before test. Graphics settings had no significant impact on test results.
CPU: i7-6600U
GPU: NVIDIA GeForce GTX 965M
RAM: 16GB
AI Benchmark:
base average time per turn (DX11 / DX12): 11.83s / 9.15s
Gathering Storm average time per turn (DX11 / DX12): 75.94s / 74.89s
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Graphics Benchmark (minimum impact settings):
base average time per frame (DX11 / DX12): 21.592ms / 25.650ms, (46.31fps / 38.98fps)
Gathering Storm average time per frame (DX11 / DX12): 81.229 / 73.738ms, (12.31fps / 13.56fps)
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Graphics Benchmark (ultra impact settings):
base average time per frame (DX11 / DX12): 57.385ms / 184.317ms, (17.43fps / 5.43fps)
Gathering Storm average time per frame (DX11 / DX12): 253.340ms / 454.538ms, (3.95fps / 2.20fps)
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DX12 doesn't seem to impact the turn time much, maybe a slight improvement, but it really breaks my gpu. I think the graphics card was designed for DX11. I noticed this in game play when the DX12 option first became available, it made the game unplayable. I always use DX11 now and usually with low impact settings on both graphics and performance settings. I guess compared to other results I've seen, my graphics card is the limiting factor which isn't surprising for a laptop.
Note on the surface book: Occasionally, the connection between the "notepad" and base of the computer is not properly detected, in that case the game will switch to the Intel HD Graphics 520 chip built into the tablet portion rather than the dedicated graphics card in the base (and might remain as the default gpu until switched back). This obviously has a significant impact on game performance which confused me in early days. It leads to things like the game turn passes normally but things like scrolling across the map take forever. I always check my graphics settings in-game to make sure it's set to the NVIDIA card before starting my game.