Virtualization technology enables a single computer to run multiple operating systems and applications in independent partitions. Both the AMD socket AM2 Athlon64 FX-62 and X2 5000+ processors support 'AMD Vitualization' technology in-chip. With virtualization, a computer system can function as multiple “virtual” systems, the in-chip hardware virtualization logic simply improves software stability and performance.

As exciting as this all sounds, the tools necessary to take advantage of this are absent from the desktop marketplace at the moment, although software virtualization packages like VMware have been around for years. Moving the capabilities of virtualization from software into hardware is seen as a way to add flexibility into processors, which for the most part aren't seeing demand increase in step with their clock speeds anymore.

Hardware Virtualization has its roots in Microsoft's Palladium initiative, where it indefinitely stalled. Both Intel and AMD have pressed ahead and implemented the feature support into the latest generation of processors.

The main drawback of software virtualization is that operating systems expect to have exclusive access to X86 architecture. In programming geek talk, OS's require Ring 0 access because that's what the hypervisor needs, and we all know the hypervisor is the master OS that hosts all the virtual machines. Uh....right?

With modern X86 architectures, there are a total of four ring levels, each of which gives less access to the hardware. For instance, WindowsXP would run at Ring 0, while Microsoft Word would run at Ring 3. Less access to the hardware makes sense since it means only the operating system has control of vital systems. Issues arise with conventional Virtual Machines when vitalizing another system, because that software program is also an operating system that is demanding Ring 0 access. As you can imagine, sorting all this out is why virtualization in software has not really trickled down to the desktop level.

To circumvent these issues in WindowsXP, the hypervisor intercept's the Ring 0 code from the virtualized OS and emulates a response. Unfortunately, this emulation requires a huge amount of computing power, which when emulating an entire operating system can severely slow a computer system down.

AMD's hardware Virtualization instructions build in privileges beneath the Ring 0 level (essentially Ring -1) which is intended to be used by the virtualization hypervisor. This way the virtualized operating systems can get Ring 0 access without the need for the hypervisor to interfere. It also improves performance as there will be less of a need for software emulation, however it's not completely eliminated since the hypervisor still needs to juggle the access to the memory controller and I/O between each virtualized machine.

At the moment, this largely an academic exercise for desktop users so let's move onto something affecting computer systems today - energy efficiency.