Isn't loongson older than riscv by more than a decade?
> Loongson moved to their own processor instruction set architecture (ISA) in 2021 with the release of the Loongson 3 5000 series.
So, again, the question is - why just not switch to RISC-V at this point?
...unless this isn't actually very different from MIPS, and is just a renamed clone of MIPS, but they're pretending like it isn't? (Which would answer my question.)
As for why bother, the goal of the project is Chinese independence from Western tech. Therefore it must be "different" but not different enough to cause much actual work or problems.
Think of it as an ISA with Chinese characteristics.
so the question is basically the opposite: why riscv when MIPS already existed and was being used by third parties?
MIPS, POWER, and SPARC, AIUI - all open enough that you could make your own processor using them.
I don't know much about the differences, but the system of standardized extensions is pretty cool and makes the same base architecture applicable to a wider range of applications.