EduMIPS64 (aka edumips) is a cross-platform MIPS 64 ISA simulator. It can be used to run and debug MIPS programs that are written using the MIPS64 instruction set. It supports visual debugging and lets you see what instructions do in the pipeline.
JTAG base library, ARM7TDMI and MIPS debugger stubs for GDB.
Extendable architecture to add JTAG device drivers, debuggers, and custom JTAG applications.