Mathcad Prime 1.0 has SI, USCS and CGS Unit System.
I think better to have: SI, USCS and Note Unit System.
Why?
1. CGS Unit System in Mathcad Prime 1.0 is not CGS Unit System (physicists like it). It is only one variant of SI.
See CGS Unit System in Mathcad 14. It is not quit correct CGS Unit System but it has stat units for example.
See too
http://en.wikipedia.org/wiki/Centimetre_gram_second_system_of_units2. When we not use units by calculations better switch is off.
Val
http://twt.mpei.ac.ru/ochkov/v_ochkov.htm