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 New data from research group IDC shows Advanced Micro Devices gained on arch rival Intel in the first quarter PC microprocessor market. There is of course still a huge gap between the two — Intel earned a 77.3 percent unit global market share, a loss of 4.7 percent, while AMD held 22.3 percent, a gain of 4.6 percent — but it’s all the more interesting given the intrigue swirling around the two companies.

EU antitrust regulators are expected to issue a ruling Wednesday that Intel illegally paid PC makers to postpone or cancel the launch of products using chips made by AMD, sources have told Reuters. The European Commission believes the violations occurred during a period stretching back eight years, the sources said. Intel could be hit with a sizable fine.

Intel, with revenue of $37.6 billion in 2008, dominates the microprocessor market. AMD posted revenue of $5.8 billion in 2008.

Also of note in the IDC research is fresh data on Intel’s Atom netbook processor. Shipments fell 33% quarter-over-quarter, indicating that equipment manufacturers held plenty of Atom inventory coming into the new year, IDC said. The group estimates Atom made up 21 percent of Intel’s mobile PC processor shipments in the quarter and 6.5 percent of its mobile PC processor revenue.

Overall, PC microprocessor unit shipments declined 13 percent from last year, while market revenue slid 25.1 percent, IDC said.