I switched from a 4K 165 Hz Samsung monitor to a Lenovo Legion monitor with a higher refresh rate, expecting better performance at 1920×1080. Instead, CS2 has dropped from around 200 FPS at my previous resolution to barely 100 FPS, and the lower frame rate is much more noticeable on the new display. The monitor is connected with HDMI, and I believe the cable is plugged into the graphics card rather than the motherboard. What could cause lower FPS at 1080p, and how can I fix it?
2 Answers
The connection and monitor settings are worth checking too. Confirm that the HDMI cable is plugged directly into the graphics card, not the motherboard, and verify in Windows and the monitor menu that the display is actually running at its maximum refresh rate. Try DisplayPort if the monitor and GPU support it, since it can avoid HDMI bandwidth or compatibility limitations. Compare CS2 with the same graphics settings as before and check for an in-game frame limit.
At 1080p, CS2 may be limited by your CPU instead of your graphics card. Lowering the resolution reduces the GPU workload, but it does not help if the processor is already maxed out. Check CPU and GPU usage, temperatures, clock speeds, and whether an FPS cap or V-Sync is enabled. Also make sure CS2 is using the dedicated GPU and that your drivers are current.
So if the CPU is the limit, is there a setting or fix that can improve the FPS?

The old display used DisplayPort, while the new one is connected over HDMI, so testing DisplayPort would be a good next step if it is available.