With Pascal Ahead, A 16-Way Recap From NVIDIA's 9800 GTX To Maxwell
Now some games that are weak by today's standards and hardware, but at least end up allowing for some more perf-per-Watt data to compare to the 9800GTX.
Xonotic isn't very demanding on modern GPUs, especially at 1080p, but provides at least more data we can compare to the older GPUs with the game still running on a GeForce 9800GTX.
Still running the open-source Tesseract game was used for similar reasons to running Xonotic with getting more data back to the 9800GTX for seeing how far the power efficiency has improved generation after generation.
Some interesting data from Furmark :)