Changes in quarterly market share for PC microprocessors don’t usually raise our eyebrows. But the first quarter results from market researcher IDC are interesting because Advanced Micro Devices has finally reversed five quarters worth of market share losses to Intel .

While the market share change is small, it can add up to a lot of dollars. AMD hit 25 percent market share a few years ago during the heyday of its Opteron server chips. It was making a ton of money, from an AMD point of view. Then it lost the performance crown to Intel and its share started shrinking. With that, AMD suffered some huge losses for the past two years.

Meanwhile, Intel can point to the market share and argue that it isn’t engaging in monopolistic practices. That’s timely, considering that the European Union’s antitrust regulators are about to levy a huge fine against Intel.

AMD’s share of the microprocessor market shipments hit 22.3 percent during the first quarter of 2009, an improvement of 4.6 percentage points over the fourth quarter of 2008. Intel lost 4.7 percent of the market, resulting in market share of 77.3 percent, according to market researcher IDC.

IDC said AMD had a pricing advantage over Intel and a strong increase in desktop shipments. AMD launched a couple of rounds of new chips in the first quarter that helped close a performance gap. Meanwhile, Intel’s customers held back on purchases as they tried to get rid of excess inventory, particularly in mobile microprocessors.

AMD now has 15 percent of the mobile processor market, up 4.7 percentage points from the fourth quarter, while Intel’s share dropped to 84.3 percent from 89.1 percent. AMD gained 3.8 percentage points in desktop chips. AMD lost 1.2 percentage points of the server and workstation chip markets.

Worldwide, microprocessor shipments were 65 million. That was down 11 percent from the fourth quarter and 13 percent from a year ago. Intel’s chief executive, Paul Otellini, said recently that Intel’s inventory of unsold chips fell dramatically and as a result he believed the company had gotten through the worst of the recession.