Difference between Virtuoso_Acceler_Parallel_sc and Virtuoso_Multi_mode_Simulation

Hi,

For running simulation, Spectre typically uses licenses from  Virtuoso_Multi_mode_Simulation pool. We have seen that with +mt=1, +aps license are picked up from Virtuoso_Acceler_Parallel_sc. What is the difference between these two licenses? Can APS run without Virtuoso_Acceler_Parallel_sc and take licenses from Virtuoso_Multi_mode_Simulation? 

Please can someone shed some light in this license options. 

PS: I have very less knowledge on the various license features Spectre provides.