Many embedded systems will offer JTAG ports for debugging. Most commonly these are connected to a host workstation running GDB via the parallel port or USB.

In the past users would implement a custom target interface in GDB to drive the JTAG interface directly. However with RSP it makes more sense to write a RSP server program, which runs standalone on the host. This program maps RSP commands and responses to the underlying JTAG interface.

Logically this is rather like a custom gdbserver, although it runs on the host rather than the target. The implementation techniques are similar to those required for interfacing to a simulator.

This is one situation, where using the pipe interface is sensible. The pipe interface is used to launch the program which will talk to the JTAG interface. If this approach is used, then debugging via a simulator should also use a pipe interface to launch the simulator, thus allowing the debugging experience to be the same whether real silicon or a simulator is used.