Once, the world’s richest men competed over yachts, jets and private islands. Now, the size-measuring contest of choice is clusters. Just 18 months ago, OpenAI trained GPT-4, its then state-of-the-art large language model (LLM), on a network of around 25,000 then state-of-the-art graphics processing units (GPUs) made by Nvidia. Now Elon Musk and Mark Zuckerberg, bosses of X and Meta respectively, are waving their chips in the air: Mr Musk says he has 100,000 GPUs in one data centre and plans to buy 200,000. Mr Zuckerberg says he’ll get 350,000.