Not Sun but Sun Labs. Ivan's Sutherland, Sproull and Associates was bought by Sun in 1990 to become the seed of the new Sun Labs. About register windows, overf

Not Sun but Sun Labs. Ivan's Sutherland, Sproull and Associates was bought by Sun in 1990 to become the seed of the new Sun Labs. About register windows, overflows and underflows generated traps to the operating system, and for the combination of Sparc version 8 and SunOS that meant thousands of clock cycles. That was improved in later products. Berkeley's RISC I to IV all had register windows but RISC-V doesn't with the argument that we have far better compilers now. Altera's NIOS processor had register windows which were dropped in NIOS II because it made the processor smaller without reducing the performance too much. The AMD 29000 had a more flexible register window scheme and the Itanium a very complex scheme. Computer history is often more like a spiral than a line and old ideas that have become bad might be good again in the future. With out-of-order execution and register renaming you might once again get better performance out of a binary with register windows.