By Harshita Mary Varghese

(Reuters) -Advanced Micro Devices and Super Micro Computer led a selloff in chip stocks on Wednesday after their earnings disappointed investors who had piled into the sector on optimism about AI.

AMD slumped nearly 10% and was on course to lose more than $21 billion in market value.

Its forecast of $4 billion in AI chip sales for 2024 fell short of the high expectations of Wall Street investors following larger rival Nvidia's massive forecasts over the past year.

Super Micro Computer, whose 150% stock jump this year has outpaced even gains in Nvidia, dropped more than 16% after its third-quarter revenue missed estimates amid questions over the profitability of a new line of servers.

The Philadelphia Semiconductor index tumbled 3.5%.

Nvidia fell 5.7%, while Micron Technology lost 2.9% and AI-linked chip firm Marvell Technology slid 3.6%.

"As the market is shifting more towards risk-off over the last couple of days, it's not shocking that unless these companies are beating earnings by a mile that some of the hot air is coming out of them for now," said Russell Hackmann, president of Hackmann Wealth Partners.

Executives of both AMD and Super Micro Computer said supply constraints were hampering their efforts to capitalize on demand for equipment powering the boom in generative AI.

"Stepping back, AMD has several customers who are all trying to ramp MI300 (AI chip) very quickly. This is stressing the supply chain to a certain extent," said analysts at TD Cowen.

"However, from a demand perspective, customer engagement is in fact increasing, not only for MI300X but its successor products."

Several analysts were still positive on AMD, saying easing supply chain constraints should allow the company to increase its share of the AI chip market and potentially reap billions of dollars in revenue.

At least 10 analysts lowered their price target on AMD, while eight raised their view, according to LSEG data. Super Micro saw three price target increases and two cuts.

Shares of Apple suppliers Qualcomm and Qorvo fell 0.7% and 3.4%, respectively, ahead of their quarterly reports on Wednesday after the bell.

(Reporting by Harshita Mary Varghese in Bengaluru; Additional reporting by Shashwat Chauhan; Editing by Krishna Chandra Eluri and Shounak Dasgupta)