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> processor or SoC contains not only RISC-V core I don't think most RISC-V cores are open source either. Remember it's not the CPU that is open source by defau
by mtgx 8y ago
> processor or SoC contains not only RISC-V core
I don't think most RISC-V cores are open source either. Remember it's not the CPU that is open source by default but the instruction set architecture.
I only know of lowRISC developing open source CPUs. Not sure if SiFive's cores are also fully open source.
https://www.lowrisc.org/ https://www.lowrisc.org/
https://www.sifive.com/ https://www.sifive.com/
- rwmj 8y agoSiFive's cores are Rocket, which is open source. lowRISC is based on Rocket too. SiFive include proprietary IP for DDR4, ethernet PHY and other things, although I'm pretty sure they'd jump at the chance to replace those bits with open source equivalents if they existed. As for your claim "I don't think most RISC-V cores are open source" it depends how you define "most", but it's a complicated picture. There are competitive open source cores (Rocket for in-order, BOOM for OoO, Pulpino, PicoRV32). There are also several completely proprietary designs, as there should be, such as Western Digital's two different 32 bit RV32 core designs which we expect will ship a billion units next year.
- makomk 8y agoAs far as I can tell, SiFive refuse to say what open source code (if any) their commercial cores such as the E31 are based on, or what changes they've made to it if it is based on open source code. See https://forums.sifive.com/t/more-details-for-e31-core/1165 https://forums.sifive.com/t/more-details-for-e31-core/1165 Basically, it's a proprietary blob which you don't know the internals of just like ARM. They've confirmed that U54 and some of their FPGA-only cores are based on Rocket, but those aren't the cores they're offering commercially.