NVIDIA GPU System Processor
The GPU System Processor is NVIDIA’s name for the component on each GPU that handles system-level functions such as power management, thermal monitoring, and other housekeeping tasks. nvidia-smi talks to this to retrieve its data without disturbing the workload being processed by the GPU.
Some documentation on GSP can be found here: Chapter 42. GSP Firmware (nvidia.com)
AMD System Management Controller
AMD’s version of the GSP is called SMC.