I switched from a 4K 165 Hz Samsung monitor to a Lenovo Legion monitor with a higher refresh rate, expecting 1080p to give me more FPS. In CS2, though, I used to get around 200 FPS at 4K—or possibly 1440p—and now I can barely reach 100 FPS at the new resolution. The lower frame rate is much more noticeable because of the monitor's higher refresh rate. My old monitor used DisplayPort, while the new one is connected with the HDMI cable that came with it. The cable is plugged into the graphics card, not the motherboard. What could be causing the lower FPS, and how can I fix it?
2 Answers
At 1080p, the graphics card has less work to do, so CS2 may become limited by your CPU instead. Check CPU and GPU usage while playing, along with temperatures and clock speeds. If the CPU is near full usage while the GPU is sitting well below 90–100%, lowering the resolution further will not improve performance. Close background programs, verify that CS2 is using the correct performance settings, and check for CPU throttling.
The connection and monitor settings are also worth checking. Confirm that the HDMI cable is plugged directly into the graphics card, not the motherboard, and select the monitor’s maximum refresh rate in Windows and in the game. Compare the actual resolutions and refresh rates you used before, since 4K, 1440p, and 1080p can easily get mixed up. Also test DisplayPort if the new monitor supports it, update the graphics driver, and make sure no frame-rate cap, V-Sync, or power-saving mode is limiting CS2.
I was using DisplayPort on the old screen and the new one is on HDMI, so I’ll compare the settings and try DisplayPort if it’s supported.

So if the CPU is the limit, is there anything specific I can change to get the FPS back up?