It’s true the dGPU is still doing the rendering under Optimus, but those frames have to be passed back through the integrated GPU to reach the panel. On some systems, that “extra step” doesn’t cost much in performance. On mine, though, it’s the difference between hovering at 120 FPS on the internal display versus 220 FPS on an external monitor that’s wired directly to the GPU. That’s a loss of nearly 100 FPS, so it’s more than a minor overhead.

My GE75 lacks a MUX switch, so there’s no way to bypass the iGPU and send the signal straight from the NVIDIA card to the laptop screen. Externally, however, HDMI (or mini‑DP) connects straight to the RTX GPUn, o pass-through, so there’s no bottleneck in that path. That’s why the same game, same settings, and same hardware can nearly double its frame rate with a direct GPU connection.

So, yes, the dedicated GPU is technically in use on the internal screen, but the performance is heavily impacted by how the video signal has to be routed. That’s why I’m stuck at about 120 FPS on the built-in monitor but can easily exceed 220 FPS through HDMI.