Patterson and Hennessy were in competition with each other, at different universities. It's only much later they wrote text books together. Patterson says RISC

Patterson and Hennessy were in competition with each other, at different universities. It's only much later they wrote text books together. Patterson says RISC-V is derived from RISC-I and RISC-II. I think this doesn't really old water -- at least no more so than any other RISC. RISC-I and RISC-II had condition codes and register windows, like SPARC. RISC-V doesn't have either, like MIPS. The RISC-V assembly language is also very similar to MIPS. RISC-II had both 16 and 32 bit opcodes (as did IBM 801, and Cray designs) and RISC-V has inherited this (but also following the great success of ARM Thumb2).