MIPS, the Microprocessor without Interlocked Pipeline Stages, is a RISC microprocessor architecture developed by MIPS Computer Systems Inc., founded in 1984 by a group of researchers from the Stanford University.
After use by Sgi in state-of-the-art workstation and server systems, it is nowadays one of the most used embedded CPU architectures.
MIPS was one of the first companies to extend their CPUs to 64-bit in the 1990s.
Used developing and using T2 just for fun on Sgi O2 and Octane for over a decade, MIPS64 support is probably production quality.