> Honestly, I don't understand why there needs to be another CPU in the system. There are tons of processors in modern systems. Most separate chips for control

> Honestly, I don't understand why there needs to be another CPU in the system. There are tons of processors in modern systems. Most separate chips for controlling sub-systems have them, like DRAM, NICs, USB, keyboards, monitors, storage devices, video cards, etc... The reasons are performance and flexibility - when separate components act like remote hosts, the device manufacturer can divide up work between the OS driver (main CPU) and target system as desired.