On SGI IRIX, the thread library depends on which compiler is used.
The o32 ABI compiler comes with a run-time library based on the
library. Thus kernel-level capabilities such as nonblocking system
calls or time slicing can only be achieved reliably by specifying different
sprocs via the pragma
See the GNAT Reference Manual for further information.
The n32 ABI compiler comes with a run-time library based on the kernel POSIX threads and thus does not have the limitations mentioned above.