According to an article at Wired, a Silicon Valley startup called Transitive Corporation claims to have written an emulator which can run an application written for any platform on another platform (for example, a Windows application on a Mac) with almost no hit in performance. The company claims that this software will eliminate the need to port applications, even saying that the application will allow current x86-based Microsoft Xbox titles to run on the next generation PPC-based Xbox. From Wired:

A Silicon Valley startup claims to have cracked one of most elusive goals of the software industry: a near-universal emulator that allows software developed for one platform to run on any other, with almost no performance hit.

Transitive Corp. of Los Gatos, California, claims its QuickTransit software allows applications to run "transparently" on multiple hardware platforms, including Macs, PCs, and numerous servers and mainframes.

"This opens up a whole new world of things you can do, because previously software was tied to (a) particular processor," said president and CEO Bob Wiederhold. "It gives you access to a much greater diversity of software."

The company claimed QuickTransit eliminates the need to port software from one platform to another. Software applications written for one platform will run on almost any other, without any modifications to the underlying program.

You can read the full article at Wiredis site.