(Reuters) - Shares of Nvidia and other technology heavyweights fell late on Wednesday, a discouraging sign for investors betting that a strong forecast from the dominant seller of AI chips would fuel fresh gains in Wall Street's most valuable companies.

Nvidia dropped 6% and lost over $180 billion in stock market value following its earnings report, this week's centerpiece event on Wall Street, while a handful of other AI-related companies shed around $100 billion in combined value.

It forecast third-quarter gross margins that could miss market estimates and revenue that was largely in line.

Shares of Broadcom and Advanced Micro Devices were each down about 2%. Microsoft and Amazon each dipped almost 1%.

Surging demand for its AI chips helped Nvidia crush consensus analyst estimates for several quarters, a trend that led investors to expect the company to exceed forecasts by higher and higher margins.

"They beat but this was just one of those situations where expectations were so high. I don't know that they could have had a good enough number for people to be happy," said JJ Kinahan, CEO of IG North America and president of online broker Tastytrade.

The lackluster response to Nvidia's earnings report could help set the tone for market sentiment heading into what is historically a volatile time of the year. The S&P 500 has fallen in September by an average of 0.8% since World War Two, the worst performance of any month, according to CFRA data.

Investors are also watching next week's U.S. employment report for signs on whether the labor market weakness that roiled stocks in early August has dissipated. If Wednesday's late-day dip in Nvidia shares extends into Thursday, it would be well short of the 11% price swing the options market had priced for the shares, according to data from options analytics firm ORATS.

Optimism about AI technology, in part due to Nvidia's explosive growth, has fueled gains on Wall Street over the past year.

However, investor confidence in that rally has wavered in recent weeks over concerns about increases in already hefty spending by Microsoft, Alphabet and other major players in the race to dominate emerging AI technology. Nvidia forecast revenue of $32.5 billion, plus or minus 2%, for its fiscal third quarter, compared with analysts' average estimate of $31.8 billion, according to LSEG data. The Santa Clara, California-based company expects adjusted gross margin of 75%, plus or minus 50 basis points, in the third quarter.

Analysts on average forecast gross margin to be 75.5%, according to LSEG data. Nvidia's stock dropped 2.1% in Wednesday's session, ahead of its report. It remains up about 150% so far in 2024, making it the biggest winner in Wall Street's AI rally.

(Reporting by Noel Randewich in San Francisco; Additional reporting by Saqib Ahmed in New York; Editing by Ira Iosebashvili and Lisa Shumaker)