Volunteer computing is a promising type of distributed computing where individuals donate computational resources of their devices for the needs of research projects. Berkeley Open Infrastructure for Network Computing (BOINC) is the most popular platform for volunteer computing, which hosts dozens of projects in such areas as medicine, astrophysics, climatology, and others. To be able to test hypotheses and make changes to the platform, developers need a platform simulator. This work presents BoSS, a comprehensive and performant simulator of BOINC platform. It models all the key components of the client and server parts of the platform while preserving their key logic. In comparison to other simulators, BoSS demonstrates higher performance, supports modeling multi-core clients, and implements the latest server and client logic.