Third-quarter earnings at Altera ( ALTR) fell 6% year over year, but still managed to top analysts' estimates on Monday.

But the company cautioned investors that it may face more tough times ahead, warning that sales and earnings may come in significantly lower than Wall Street's estimates in its current quarter.

Investors shrugged off the news in trading after the company's earnings release. In after-hours exchanges, Altera's stock was recently off 6 cents, or less than 1%, to $17.67.

The chipmaker earned $77.8 million, or 21 cents a share, in the just-completed period. That was up from $67.6 million, or 18 cents a share, it earned in the second quarter, but down from the $83.1 million, or 22 cents-a-share profit it posted in the year-ago period.

Analysts were expecting the company to earn 20 cents a share on sales of $291.3 million in its third quarter.

Sales grew 2% sequentially from the second quarter and 10% year over year to $291.5 million. But the company's gross margin -- the difference between what it charges customers for its products and its direct costs to make them -- fell to 66.5% of sales from 68.3% in the second quarter and 69.4% in the third quarter last year.

The company had predicted that it would post sales of between $288.4 million and $294 million for the quarter. Altera last month reduced its gross margin target to 66% to 67% of sales from a previous range of 68% to 69%, blaming a permanent cut in sales of certain high-margin chips.

The company had not given earnings-per-share guidance.

In the current, fourth quarter, Altera expects sales to range from down 2% sequentially to up 2% sequentially, meaning revenue ranging from $285.7 million to $297.4 million. The company predicted that gross margins would remain at about 66% of sales.

Although the company did not provide a specific earnings target, its guidance implies earnings of about $55 million to $61 million, or 14 cents to 16 cents a share, assuming that its share count remains about the same.

Wall Street predicted that the company would earn 21 cents a share in the current period on $302.9 million in sales.

Shares of Altera closed regular trading up 37 cents, or 2%, to $17.73.