@grahamperrin Optimus is a trademark of NVIDIA for their implementation of hybrid graphics.And other manufacturers like AMD calls almost the same thing differently.From the CPU-side of the view, PRIME is the underlying interface for iGPU and dGPU (not limited with NVIDIA) to offload heavy graphics tasks to mighty dGPU, mainly using efficient (but poor in performance) iGPU.Before Austin's port of nvidia-drm.ko appears, the only "working" way to achieve hybrid graphics was to use VirtualGL, with configuring individual "screen" for iGPU and dGPU respectively, and screen rendered by dGPU was needed to be transferred to another (for iGPU) with software BitBlt, as physical framebuffer cannot be shared with this method.And current implementation of nvidia-drm.ko relies on PRIME to work. Without PRIME, there's no way (arbitrations) for dGPU to access (part of) physical framebuffer of iGPU.See detailed and precise info by Austin here. https://badland.io/prime-configuration.md
