I think x86 chips with Intel Active Management has the 'Management Engine' which runs an ARC processor with a ThreadX RTOS on it. It even has it's own network interface separate from the rest of the CPU. As far as I can tell this is for Enterprise users who need to manage the PC's and Rack computers remotely, even when the OS dies.
Most motherboard vendors also thrown stuff onto enterprise motherboards for doing things remotely. They can have issues: https://www.youtube.com/watch?v=GZeUntdObCA