ftp://ftp.qnx.com/usr/free/qnx4/os/development/sysdbg.tgz
…for those who are looking for some low-level QNX4 system interface
description. Nice presentation from QNX2000 with lot of information for
inquired minds 
ps: some questions asked here not so long ago are answered in this
publication.
–
Ian Zagorskih
Novosibirsk Branch of TyumenPromGeophysics
R&D Department
Phone: +7-3832-334210, 331718