Applications compiled with IRIS Performer 2.0 using IRIX 5.3 will
  run unmodified across all SGI platforms.  For best performance, use
  IRIS GL with RealityEngine and other pre-Impact systems and use
  OpenGL for Impact and post-Impact graphics hardware.
  OpenGL-oriented systems provide the IGLOO (Iris GL on OpenGL)
  portability layer to execute IRIS GL applications, but it is not
  the maximum performance route.  Performance oriented developers are
  advised to generate both IRIS GL and OpenGL executables, by linking
  with the API-compatible IRIS Performer 2.0 IRIS GL and OpenGL
  libraries.  In this way, you can assure optimum performance across
  present and future graphics systems. For OpenGL development on
  RealityEngine with IRIX 5.3, patch 154 (or a superseding patch) is
  recommended for performance and features.

  IRIS Performer 1.2/IRIX5 contains a single version of libpr for all
  machines.  Applications built with Performer 1.2 for Irix 5.2 are
  fully compatible across machines and can run on any graphics type
  without relinking.

  In IRIS Performer 1.0, 1.1, and 1.2/IRIX4, libpr is platform-
  specific with one of two versions installed depending on whether
  the machines is a RealityEngine or not.  Binaries linked on
  non-RealityEngine machines will run on a RealityEngine, but not all
  features will be available.