SANTA CLARA, California (Reuters) - Celestial AI, one of several Silicon Valley chip startups aiming to crack a key speed constraint in artificial intelligence, said on Tuesday it has raised an additional $250 million in venture capital, bringing its total raised to date to $515 million.

Celestial AI Inc., a startup that develops optical technology for linking chips, has raised $250 million in funding at a $2.5 billion valuation. The Series-C1 investment comes a year after the company’s previous raise.