IRIX version 5.0-5.2
IRIX 5.0 marked the transition to ELF binaries and dynamic libraries (with DSOs or dynamically shared objecte). IRIX 5 also marked the release of patchsets rather than the maintenance upgrades of earlier versions. Perhaps the most obvious change for the user is the introduction of the Indigo Magic user environment, which would be maintained with little change throughout all subsequent versions of IRIX. Indigo Magic was released first with Indy IRIX 5.1, and then was included in the all-platforms IRIX 5.2 release. IRIX 5.0 and the version of IRIX 5.1 released with other machines included the older IRIS Workspace user environment as used in IRIX 4.0.x.
IRIX 5.0 and IRIX 5.1 should be avoided if possible. They were the subjects of the infamous SGI memo and the source of the joke "an Indy is an Indigo without the go." They have a high population of bugs and memory leaks. IRIX 5.2 is the last release of IRIX to work across the entire MIPS-based 4D series as of its release, but for machines that can run it IRIX 5.3 is a better choice, especially since SGI makes the IDO for IRIX 5.3 freely available.