Intel (Nasdaq: INTC), the No. 1 chip maker, warned third-quarter sales would be far below prior estimates, chopping as much as $600 million from predictions.

The Santa Clara, Calif., chip maker said revenue will likely be around $13.2 billion, rather than in the range of $13.8 billion to $14.8 billion it had expected. Intel said revenue could be as much as $300 million lower or higher than the new target. Intel had expected that demand for new Ultrabook chips, as well as sales to consumers for back-to-school uses, would be stronger.

Analysts said Intel may have been the victim of customers avoiding purchases ahead of next quarter's release of Windows 8 by Microsoft (Nasdaq: MSFT), the No. 1 software company.

Vijay Rakesh, of Sterne Agee, said big PC makers likely reduced inventory ahead of Windows 8 as well as lower demand in general for PCs. Last month, market researchers Gartner and IDC both predicted anemic growth in the overall PC sector this year as consumers shift to tablets.

The surprise news sent Intel shares down 90 cents, or 3.6 percent, to $24.19 by the close of Friday trading.

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