EduMIPS64 is a free (as in free speech) visual and cross-platform MIPS64 CPU
Simulator.

The simulator was written in order to support Computer Architecture students
with a free and cross-platform tool that allows them to run programs written
in the MIPS64 assembly dialect and see how the CPU behaves during the
execution, experimenting with various aspects of low-level programming
that they learn throughout the course.

EduMIPS64 started as a GPL Java port of WinMIPS64, a Windows-only MIPS64
simulator, but independently evolved soon after into a stand-alone
open source application.