With Red Hat, Novell - and now Intel, thanks to its $884m acquisition of Wind River - all crowding into the real-time Linux space, Concurrent has to keep on its toes and keep its RedHawk Linux, well, current. With RedHawk Linux 5.4, announced Tuesday, Concurrent is slipping into Linux 2.6.31 and offering full compatibility with Red Hat Enterprise Linux 5 update 4. That's because RedHawk is a tweak on Red Hat, adding real-time extensions and other goodies cooked up by Concurrent to make it different from Red Hat's own Enterprise MRG real-time Linux.