(Reuters) - Shares of Advanced Micro Devices ( AMD ) and Super Micro Computer ( SMCI ) sank on Wednesday, sparking a selloff in chip stocks, after their earnings disappointed investors who have piled into the sector on hopes rising AI investments would boost demand.

AMD was down more than 6% in premarket trading, and is on course to lose more than $16 billion in market value.

Its forecast of $4 billion in AI chip sales for 2024 fell short of Wall Street's lofty expectations, having been used to Nvidia's ( NVDA ) massive forecasts over the past year.

Super Micro Computer ( SMCI ), whose near-200% stock jump this year has outpaced even gains in Nvidia ( NVDA ), tumbled over 11% as its third-quarter revenue missed estimates amid questions over the profitability of a new line of servers.

Executives of both AMD and Super Micro Computer ( SMCI ) 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."

Other AI-linked chip firms also traded lower, with Marvell Technology ( MRVL ), Micron Technology ( MU ) and Nvidia ( NVDA ) down between 1.5% and 2.5%.

The stocks have widely outperformed the benchmark S&P 500 index this year and powered a 11% jump in the Philadelphia Semiconductor Index.

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.

"Against a very large AI computing TAM (total addressable market), we believe AMD is well on the way to cementing its position as the de facto alternative to Nvidia's ( NVDA ) leadership position," analysts at TD Cowen said.

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.