SAN JOSE, Calif.--AMD's quad-core Opteron processor, code-named Barcelona and due in mid-2007, includes features to speed up virtualization.

Virtualization, a hot subject today as companies try to make servers more efficient, lets a single server run multiple operating systems. But virtualization software called a hypervisor, which oversees the operating system access to the hardware, poses performance problems compared to operating systems running on their own.

Barcelona has specific features to deal with some of those performance issues, Ben Sander, a principal member of AMD's technical design staff, said in a speech Tuesday at the Fall Processor Forum here.

One performance problem comes because operating systems are accustomed to handling a part of the chip called the translation lookaside buffer, or TLB, which converts an operating system's relative memory addresses into the actual addresses used by the hardware. But with a hypervisor actually in charge of memory, virtualization adds a second level of translation to the task.

To deal with the situation, hypervisors use software called shadow paging. "It's complex to implement and can be fairly slow," Sander said. Barcelona technologies, including "nested page tables" and the caching of memory addresses, speeds up the memory issue.

That's significant, given that such memory issues can occupy as much as 75 percent of the hypervisor's time, he said.