The Argonaut 5, the 599 Eagle and 539 Argo VI are a distinct branch of the Ten-Tec product line.
For context, the Pegasus/Jupiter transceivers used a single DSP/UI processor and the Orion(s) used 3 processors (2x DSP, 1x UI) they were both designed around a dense, complex PCB for the Digital section. These new radios take a different approach by creating separate DSP and User Interface Controller boards that could be plugged into a main motherboard that took care of all the digital interconnect. These plugin boards came to be know as the SPU (Signal Processing Unit) which contained the DSP processor and the CPU board which contained the user interface and hardware control signals.
The CPU board firmware, in addition to running the main code, contained the DSP firmware which would be downloaded to the SPU the moment the radio was turned on.