One interesting advantage of RISC-V is extensibility. RISC-V has: - Two major opcodes reserved for custom extensions (four if you aren't using RV-128, which yo

One interesting advantage of RISC-V is extensibility. RISC-V has: - Two major opcodes reserved for custom extensions (four if you aren't using RV-128, which you probably aren't); - Easy-to-decode variable length encoding, not only for half-size instructions (normally the C standard extension), but also for longer instructions; IIRC, the HWACHA extension uses that for 48-bit vector instructions. That is, RISC-V can be used as a base ISA for a your own custom ISA, while keeping the same tooling and being able to reuse common code. Need a coprocessor with extra DSP instructions? No problem, get a 64-bit RISC-V core as a base and add the DSP instructions to it. Need an extremly small embedded processor to manage your complicated chip? RISC-V has a small variant, RV32E, which is the same as the normal 32-bit RISC-V but with half the registers. Don't want to wait for the B standard extension to add POPCOUNT? Make your own extension. And so on.