I don't think a MIPS version ever existed. The only public releases that ran on MIPS (6.4 and pre-SP1 6.5) only bundled a handful of Photon-related binaries, which if my memory serves were just input drivers.
There were x86 and more or less complete ARMv7, PowerPC, and SuperH ports.
There were x86 and more or less complete ARMv7, PowerPC, and SuperH ports.