A Bristol start-up building the next generation of microchips for artificial intelligence technology has raised $150m (£116m) from investors including Edinburgh's Baillie Gifford. Graphcore, founded in 2016 by Icera co-founder Nigel Toon, is now valued at almost $2bn having raised $450m from investors. Its new investors include Baillie Gifford, which has more than £200bn of assets under management, Mayfair Equity Partners and M&G Investments. Previous backers include Microsoft, BMW and Silicon Valley venture capital fund Sequoia. Graphcore has developed an intelligence processing unit, a microchip designed for artificial intelligence software.