Berkeley RISC I and RISC II had register windows, and led to SPARC. MIPS was Stanford. And, yes, they learned the hard way that register windows are a bad idea

Berkeley RISC I and RISC II had register windows, and led to SPARC. MIPS was Stanford. And, yes, they learned the hard way that register windows are a bad idea. Patterson says they did it because their compiler didn't have as good register allocation as Stanford's compiler.