But increasing interest from the big East Coast firms is no surprise. "It's the most important industry in the United States," says Sandy Robertson, Francisco Partners co-founder and éminence grise of Silicon Valley finance. "If you're not in it, you're not really in business."

The East Coast firms have occasionally stuck a toe into technology over the years, but the first serious move came in 2005 with the $11.3 billion purchase of software-services provider SunGard, by Blackstone, Bain, Goldman Sachs, and Silver Lake.

Late last year, KKR, Bain, and Silver Lake teamed up to buy 80 percent of Philips Electronics operations, renamed NXP, in a $4.3 billion deal, plus $5 billion in existing debt. In April, KKR agreed to buy First Data,

But the Blackstones and the KKRs—whose interests range widely, from auto-parts makers to women's undergarments to radio stations—have yet to show they've got the chops to enter the complicated world of high technology.

Aswatch Damodaran, a professor and tech-finance specialist at New York University, says he believes too much capital is forcing the traditional private equity firms into a market they don't understand. "If they continue in tech," he says, "it will be their Waterloo."

(Neither Blackstone nor KKR would comment about the substance of this article. A Blackstone spokesman explained: "We've been beat up by so many people, I don't think we want to talk to anybody.")

For a vivid look at the challenges, consider last December's $17.6 billion leveraged buyout of Freescale Semiconductor. A longtime division of Motorola, Freescale was spun off in a 2004 I.P.O. While Blackstone, Carlyle, and TPG were negotiating the buyout, Motorola and its then-hot Razr phone seemed to be riding high.

But just a few weeks after the deal was announced, Motorola's ugly underbelly came to the surface. The Razr was losing popularity faster than anyone thought, even as Motorola kept cutting its price. Revenues and margins both got whacked, investors waterboarded Motorola's stock, and some shareholders were calling for C.E.O. Ed Zander's head.

No one expects an easy fix, because Motorola has failed to produce a must-have successor to the Razr phone.

Motorola's problems infected Freescale, which supplies chips for the Razr and counted on Motorola for 27 percent of its revenue.