A microprocessor architecture having extendible logic. One or more customized applications are available to the instruction pipeline. The customizable applications may include software, extension logic instruction or register, dynamically configurable hardware logic, or combinations of these. In order to enable the operating system to interface with the customized extension applications, at least one software extension is provided to the operating system. When a specific extension is requested a software exception is generated by the OS. In response to the exception, the least one software extension is called to handle context switch and dynamic configuration of the extendible logic of the microprocessor.