Stay informed with free updatesSimply sign up to the Artificial intelligence myFT Digest -- delivered directly to your inbox.Lambda Labs, a cloud computing start-up that rents out servers powered by Nvidia’s artificial intelligence chips, is in talks to raise another $800mn as it looks to capitalise on the bull market around AI and the scarcity of the most advanced graphics processing units.The proposed deal would vault the company into the ranks of Silicon Valley’s best funded start-ups of rece...