Cerebras stock plummeted nearly 20% this week to its lowest price since the company's IPO in May, closing Friday at $166.43. The decline is attributed to pressure from chip giant Nvidia, which is reportedly powering a crucial piece of OpenAI's latest model with its GPUs instead of Cerebras hardware, and the expiration of post-IPO restrictions on some insider shares. Cerebras' market cap has fallen to just over $39 billion, down from $95 billion on its first day of trading.