The PCI Express specification describes two reset generation mechanisms. The first mechanism is a system generated reset referred to as Fundamental Reset. The second mechanism is an In-band Reset (communicated downstream via the Link from one device to another) referred to as the Hot Reset.
Fundamental Reset causes a device's state machines, hardware logic, port states and configuration registers (except sticky registers of a device that can draw valid Vaux) to initialize to their default conditions.
There are two types of Fundamental Reset:
Cold Reset. This is a reset generated as a result of application of main power to the system.
Warm Reset. Triggered by hardware without the removal and re-application ...