Academic RISC was designed by Patterson and Hennessy. Hennessy went off and was one of the founders of MIPS, Patterson is one of the instrumental leaders in the RISC-V space.

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).

Nice that there's both MIPS and RISC-V versions of the book:

https://www.amazon.com/Computer-Organization-Design-MIPS-Arc...

https://www.amazon.com/Computer-Organization-Design-RISC-V-A...

I guess as of today we know which one to get.