Shares in major chip companies fell sharply across the US and Asia on Tuesday as a sell-off in artificial intelligence-related stocks deepened, raising fresh doubts about the sustainability of the AI investment boom. The rout was severe enough to trigger a temporary trading halt on South Korea's Kospi index, and pushed Nvidia out of its position as the world's most valuable listed company, with Apple overtaking it instead.

South Korea's Kospi was paused after falling 8%, then dropped around 10% once trading resumed, led by Samsung Electronics and SK Hynix, both down more than 10%; the index has now lost about a third of its value since mid-June after more than doubling earlier in the year. Japan's Nikkei 225 fell almost 4.5%, while Nvidia had already dropped 5% in New York on Monday following reports it is in talks to provide around $250bn towards an OpenAI data-centre project. Some analysts have questioned whether AI investment on this scale can ever generate sufficient returns.