Earlier this year, we unstintingly dedicated some precious screen space to a preview of OnLive’s cloud-based gaming service, which many believe can usher in a new era in video games. That belief has found another taker in the form of AT&T, which is OnLive’s latest financial backer. OnLive announced yesterday that it has raised a third round of funding from AT&T, Lauder Partners, and its original investors.

The server-based gaming service promises to deliver the latest video games to any broadband-enabled PC or TV set without requiring any fancy gaming hardware.

The company is not willing to divulge the exact volume of funding. According to GamesBeat, one venture capital source speculates that funding in the third round may have topped $500 million.

“But we’re limited on what we can disclose. The valuation was quite high for a pre-revenue company. It is probably among the highest for a pre-revenue company getting funding this year. But the scope of the opportunity is high,” said Steve Perlman, OnLive’s founder and CEO.

Although a few other similar ventures are vying for what they all believe is an assured place in video game history, OnLive’s huge wealth of intellectual property – more than 100 patents and counting, coupled with the financial muscle of its backers gives it an obvious advantage. It is currently being put through its paces by beta testers.