Executable file for Silicon Graphics O2

Hi, Dear MODELLER users: Our Silicon Graphics is O2, which has operating system IRIX Release 6.3 and CPU MIPS R5000, Rev 2.1. Can anybody tell me which executable file should I download besides the modeller4-data.tar.Z? and what is the "HOSTTYPE" for O2 computer? Thank you very much. Best Regards, Chunhua Yuan