Gameshop Debugger (Gvd) - Nintendo Ultra64 Programmer's Manual

Introduction
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Originally developed to verify hardware design and enable parallel
hardware and software development, it remains useful for developing RSP
microcode in a stand-alone fashion.
It has two interfaces, a simple text window interface (rsp) and a fancy
window interface (rspg). The window interface supports source-level
debugging, which is extremely useful.

Gameshop Debugger (gvd)

The Gameshop debugger, gvd, can be used to debug RSP microcode
running on the real hardware.
Detailed instructions are beyond the scope of this document, but if you open
the "Coprocessor View" on gvd and set the program counter appropriately
you will be looking at IMEM. From here you can trace execution and
examine memory and registers.