The Real-time Extension (RTX) to Windows is based on the Windows Win32
API. Applications can be built to work in two different modes:
Windows executables that run in Ring 3 to utilize memory protection
(rts-rtx-w32).
Real-time subsystem (RTSS) executables that run in Ring 0, where
performance can be optimized with RTSS applications taking precedent
over all Windows applications (rts-rtx-rtss).