Aug 2 Reuters Advanced Micro Devices39;s shares fell about 6 on Wednesday as analysts raised concerns that the chip designer39;s targets for an artificial intelligence AI rampup may be too ambitious.

The fall came amid a broader selloff in the tech sector that saw megacap stocks fall 1.5 to 5 and the Philadelphia SE Semiconductor Index drop 3.5. Wall Street fell on Wednesday after rating agency Fitch downgraded the U.S. government39;s credit rating.

AMD39;s stock had risen 4 in extended trading on Tuesday after the company said customer interest was very high for its upcoming MI300 AI chip, which will ramp up in the fourth quarter.

AI has been a key theme in the chip sector so far this year, driving shares of chip companies and helping Nvidia become the first and only semiconductor firm to be valued at more than a trillion dollars.

Investors hope AMD will emerge with a challenger chip to Nvidia39;s most powerful AI semiconductors and help in fulfilling strong demand for chips that can power applications like chatbot ChatGPT.

AMD39;s shares have risen about 82 so far this year, compared with Nvidia39;s stock that has more than tripled in value. The Philadelphia SE Semiconductor Index has gained about 52.

AMD39;s forward pricetoearnings multiple, a common benchmark for valuing stocks, stands at 31.40.

Unless numbers get really material, soon, we fear estimates remain too high and the stock AMD looks a little stretched to us, Bernstein analysts wrote in a note….