PC and semiconductor stocks face trouble as sales growth slows. Warnings from Intel, National Semi, PMC-Sierra worry investors.

Earnings warnings from the chip industry have started to pile up. In late August, Intel cut its third-quarter sales guidance, cautioning that "revenue is being affected by weaker-than-expected demand for consumer PCs in mature markets." Not long after, there was a similar pre-announcement from National Semiconductor, which in early September said that "in the near term, slower growth in our end markets and distribution channel, along with some likely inventory reduction, will mute the seasonal growth that we would normally see in our business during this time of the year."

There were warnings earlier this month, as well, from Monolithic Power Systems and Silicon Laboratories. Last week, PMC-Sierra, known mostly for selling chips to the communications sector, cut third-quarter guidance with little explanation. Thursday afternoon, Advanced Micro Devices warned third-quarter revenue would be 1% to 4% below that of the second quarter, "due to weaker than expected demand, particularly in the consumer notebook market in Western Europe and North America."

So, is the worst over? I doubt it. CreditSights analysts Ping Zhao and Jordan Chalfin noted in a commentary last week that inventory in a number of sectors—including semiconductors, storage, PCs and distribution—has been ratcheting steadily higher. The analysts report that most tech sectors saw second-quarter inventory days rise from first-quarter levels—the opposite of the pattern a year earlier. The CreditSights analysts are particularly concerned about rising inventory at electronics distributors, warning that "any distribution inventory correction could have a negative impact to semiconductor companies' margins."