Remedy Debugger

The Remedy debugger was the first embedded system level debugger in the world. It offered many features that users take for granted today in the days when having a source level debugger was a luxury. Some of these features include:

Multiprocessor operation
Heterogeneous
Distributed
Dynamic thread view of the system
Synchronized debugging for multiple threads
Trace functions
Operating system resource displays
Source and assembly level debugging

It started as an academic research project. The results were published in one of the early papers on debugging multiprocessor systems.
The current version of the Unison Operating System continues to use both gdb and Remedy debugger.