A while back I was on a project to port a satellite simulator from SPARC/Solaris to RHEL/x64. The compressed telemetry stream that came from the satellite needed to be in big endian (and that's what the ground station software expected), and the simulator needed to mimic the behavior.

This was not a problem for the old SPARC system, which naturally put everything in the correct order without any fuss, but one of the biggest sticking points in porting over to x64 was having to now manually pack all of that binary data. Using Ada, (what else!) of course.