AMD crossed a $1 trillion market capitalisation on Monday, September 21, after its shares surged about 10% to close at $615.52 — valuing the chipmaker at roughly $1.004 trillion. It became the 14th US company to reach the milestone, according to Dow Jones Market Data.

The rally followed the strong reception of Meta’s Muse personal AI agent, which reached the top of Apple’s US App Store free chart after its September 8 launch, overtaking ChatGPT. The Philadelphia Semiconductor Index gained 4.3% for its fifth straight advance. Intel rose 12% and Arm jumped 17% on the same day.

Investors are betting that AI agents will drive stronger CPU demand. Unlike query-based chatbots, always-on agents like Muse run continuously — planning tasks, browsing and calling tools — a workload that pulls heavily on CPUs, where AMD, Intel and Arm compete with Nvidia’s GPUs.

Meta’s own shares rose more than 11%, their strongest session since April 2025. AMD shares are up nearly 200% this year, confirming its arrival in the mega-cap semiconductor club alongside Nvidia, Broadcom and Micron.