IRIX 6.1 has kernel support for COFF executables, but does not have at
  least some of the shared libraries. If you copy the needed shared
  libraries from an IRIX 6.0.1 (or perhaps 5.3) system to your IRIX 6.1
  system your COFF executable should work.

  IRIX 6.2 does not have kernel support for COFF, so you will have to
  recompile your COFF binaries. The IRIX 6.2 installation procedure will
  warn you about COFF binaries, although only on local disks; be sure to
  check machines yourself which provide binaries to IRIX 6.2 machines
  via NFS. You can find COFF binaries yourself with something like
  'find / -print | xargs file | grep COFF', or use the script
  ftp://ftp.sgi.com/support/Pipeline/coffcheck.tar.Z. See also "The End
  of COFF Support" in the Jan/Feb 1996 Pipeline.