SiFive, a chip design startup founded by UC Berkeley engineers, raised $400 million at a $3.65 billion valuation in a round backed by Nvidia and led by Atreides Management. The company designs open-source RISC-V chips as an alternative to Intel's x86 and ARM architectures, positioning itself to serve AI data centers. This is well-sourced reporting confirmed by Reuters, TheNextWeb, and Business Wire — the core facts (funding amount, valuation, lead investor, Nvidia participation, chip architecture) are all verified.