Amazon has increased its investment in AI startup Anthropic by $4 billion, bringing its total stake to $8 billion.Anthropic produces Claude, an AI assistant that competes with OpenAI's ChatGPT.The investment is driven by the need for specialized processors for training large AI models.Anthropic will use Amazon's Trainium and Inferentia chips, as well as collaborate on processor development with Amazon's Annapurna Labs division.