Indeed. The "C" extension is technically optional, but I'm not aware of anyone who has made or sold a production chip without it -- generally only student proj

Indeed. The "C" extension is technically optional, but I'm not aware of anyone who has made or sold a production chip without it -- generally only student projects or tiny cores for FPGAs running very simple programs don't have it. My estimate is if you have even 200 to 300 instructions in your code it's cheaper to implement "C" than to build the extra SRAM/cache to hold the bigger code without it.