https://youtu.be/8ZRuFaFZh5M
The monitor was the ASUS VG27AQ (max refresh of 165 Hz) with adaptive-sync enabled, and the "games" tested were CS:GO, ezQuake, and a simple UE4 build. The results were (with one exception) extremely consistent. Key findings:
- [4:24] V-Sync lag is real!
- [5:23] Capping at 165, either internally or externally, made no difference from pure V-Sync.
- [5:37] Internal caps are best
- [5:55] I found no difference between capping one frame below or three frames below the max refresh rate.
- [6:25] External caps (RTSS, NVIDIA control panel) perform near identically, and they tend to be one frame worse than internal caps
- [13:37] Full GPU utilization does dramatically increase input lag!
I was also prompted to make this video because someone in the comments suggested that adaptive-sync displays can actually beat CRTs for input lag, and he was right... in a certain set of circumstances. CRTs need consistent, fixed frame rates, which means either V-Sync or scanline-sync and their concomitant latency. So unless you can get your CRT to play nice with variable blanking, adaptive-sync displays have stutter-free motion with lower input latencies than a CRT throughout a huge FPS range, and I find that pretty cool.
Several things I didn't test were resolution scaling, external post-processing filters like Re-Shade, etc. If you want to see results for those, let me know.