[lkcl]

this is unfortunately not true (that the RISC-V ISA was designed not to require currently-valid patents). people may believe that to be the case, but it's not. from 3rd hand i've heard that IBM has absolutely tons of patents that RISC-V infringes. whether IBM decide to take action on that is another matter. they're a bit of a heavyweight, so there would have to be substantial harm to their business for the "800 lb gorilla" effect to kick in.

[jecel]

See this report about the origin of each basic RISC-V instruction:

https://riscv.org/technical/specifications/risc-v-genealogy/

Of course, the various extensions might violate current patents (I would guess that packed SIMD and cryptography extensions are particularly at risk). But the basic ISA does not use anything that was not already widely adopted by 2003.