MORRISVILLE, N.C. – The recent run on profits, revenues and surging PC sales may be coming to an end at

Global PC sales are "falling off a cliff,” J.P. Morgan analyst Christopher Danely wrote Tuesday. PC makers are facing turbulent economic waters as the continuing global economic slowdown is cutting into PC demand, Danely and another anaysts warned Tuesday.

Hewlett-Packard Co., the No. 1 PC seller, and Acer Inc., No. 3, have cut orders to suppliers of laptop parts, J.P. Morgan analyst Christopher Danely wrote. And Acer and Lenovo have cut orders to semiconductor companies, he added. As a result of his findings, Danely lowered his estimates on chip maker Intel’s 2010 numbers.

"Although there is a possibility order rates could recover, we view this as unlikely given increased inventory in the supply chain and weakening demand in the U.S. and Europe and slowing demand in China," Danely wrote in a note to clients Tuesday.

He said he expects other markets to follow.

"We expect the weakness to show up in every end market for semiconductors, just as it always has during downturns," he wrote. "We continue to be cautious on the space due to the large amount of capacity coming on line combined with softening demand."

Dell, the No. 2 PC maker, operates a huge manufacturing plant in Winston-Salem that has been kept open due to strong customer demand.

, as are profits.

Shares in Intel, AMD and Nvidia all fell after the analysts’ reports.

Barclays Capital’s Tim Luke told clients that his latest checks reveal that third-quarter PC sales "have continued to remain subdued and Intel and AMD seasonal sales guidance may prove bold."

The comments amplified fears that PC sales, which have been buoyed by intense interest in cheap laptops, are starting to slow. One reason is tightfistedness by consumers who are worried that the economy and their job prospects will stay weak.

Some semiconductor makers have reported blowout numbers – Intel, for example, booked its biggest quarterly net income in a decade in the second quarter – but in many cases their stocks have barely budged. That’s because investors have been worried that forecasts for the second half of 2010 could be too optimistic, given worries about Europe’s debt crisis and the strength of the U.S. economy’s recovery.

Intel is the world’s No. 1 maker of the "brains" of PCs. AMD is No. 2. Nvidia is a big maker of graphics chips. The stocks can rise or fall together on sweeping news about the health of the computer market.

On Tuesday, Intel shares fell 4.2 percent, or 86 cents, to $19.79. AMD shares fell 8 percent to $6.83, while Nvidia shares slipped 4.5 percent, or 43 cents, to $9.21. The Philadelphia Semiconductor Index slid 2.8 percent, or 9.88 points, to 344.17 points – a bigger drop than in the broader markets Tuesday.

Computer sales are being hurt by austerity measures in Europe, tightened spending in China and a cooling off of stimulus spending in the U.S., said analyst Tristan Gerra with Robert W. Baird & Co.

Gerra downgraded his rating on Intel’s shares to "Neutral" from "Outperform" on evidence of a sharp deceleration of PC orders in August and signs that a recovery in September is looking unlikely. One reason is PC makers bought too many chips in the first half of this year even as demand started to slow this summer, Gerra said.

"We see the weakness more so on the consumer side, even though we hear of some weakness in enterprise as well, notably from Europe," Gerra wrote in an e-mail.

One bright spot for the industry is proving to be a double-edged sword.

Apple Inc.’s iPad is eating into laptop sales but its strong showing is an encouraging sign for overall computer demand. Apple has sold more than 3 million iPads since it went on sale in April.

Get the latest news alerts: at Twitter.