Hot plug and hot swap

This chapter describes Hot Plug and Hot Swap, two approaches to the problem of maintaining mission-critical systems by allowing modules to be swapped while the system is running. Hot Plug places the burden of supporting live insertion on the platform so, that virtually any PCI board is hot plug-able. Support for live insertion includes bus isolation and power switches on the motherboard for each slot. Therefore, the operator must notify the desired system to insert or extract a board and wait for confirmation before taking the action. The Hot Plug Service provides the interface to the operator while the Hot Plug System Driver controls the platform resources. A set of Hot Plug primitives defines the essence of an API between these two elements. Hot Swap builds on the Hot Plug model but places the burden of support on the board with only minor modifications to the backplane. Hot Swap also includes a mechanism to automatically detect an insertion or extraction event, simplifying the operator's task.