SAN FRANCISCO — Don’t look now: Storm clouds are gathering over tech.

Chinese consumers have pulled back their spending, blowing a $9 billion hole in Apple’s recent quarterly revenue. China was again a culprit when Nvidia warned last month that its revenue would come in 20 percent below expectations, though the graphics chip maker also blamed slack demand from Bitcoin miners and cloud data centers.

Intel, the big chip maker, cited intensifying “trade and macro concerns” for financial results in January that did not meet expectations. And Samsung, another semiconductor powerhouse, said sales plunged 10 percent in the fourth quarter because of weakening demand for its memory chips from data centers and smartphones.

China, smartphones, Bitcoin and cloud computing have been among the major drivers of the long tech boom, which in turn has powered the global economy for the last decade. The ingredient common to all of these sectors is computer chips, which form the brains of devices and whose ubiquity means they provide early signals about changes in supply and demand.

Warnings about a sales slowdown this year have come in recent weeks from big chip suppliers that also include Taiwan Semiconductor Manufacturing Company, Micron Technology and Western Digital. It’s an abrupt reversal, coming on the heels of stellar results in 2018 for the business that gave Silicon Valley its name.