PCI controllers play a crucial role in ensuring that peripheral devices can communicate efficiently with the processor and other devices in a computer system. Without a PCI controller, devices would not be able to exchange data, and the computer would not be able to function properly.
CPU <--> Host/PCI Bridge (PCI Controller) | PCI Bus 0 | +----+----+----+----+ | | | | | Device 0 Device 1 Bridge ---> PCI Bus 1 | Device 2 pci controller