Processor Virtualization: Many Computers, One Machine

Virtualization. The term may conjure up sci-fi images of Star Trek's holodeck or virtual reality, but both AMD and Intel are putting big bets on virtualization as a CPU technology -- one that ultimately could deliver some major changes in how our home and business PCs work.
Virtualization isn't new, but few PC users are familiar with the concept because it premiered on the huge research mainframes of yesteryear and on RISC servers rather than x86 platforms. Basically, it enables users to run multiple operating systems (or instances of the same OS) on a single computer and switch between operating systems on the fly.
This is more ambitious than mere multitasking, in which different applications run simultaneously. Under Windows, for example, individual programs don't have the right to access "privileged" areas of the system such as input/output; only the kernel -- the Windows OS itself -- can tap these resources on behalf of applications, and the computer is limited to running one kernel at a time.
Virtualization is also different from Intel's Hyper-Threading Technology, though both require some special hardware features in the processor. Hyper-Threading enables a CPU to execute more than one thread or part of an application at once, but there's still only one operating system or layer between the application and the hardware. Even multiprocessor systems or multicore processors don't necessarily support multiple operating systems.
"Conceptually, virtualization really enables the user or any IT infrastructure to separate the hardware from the software in a logical format," explains David Auster, division marketing manager in AMD's commercial marketing organization.
"Traditionally, we've had a very one-to-one relationship between the hardware and the operating system -- say, Windows. [Virtualization] allows you to have a one-to-many relationship between the hardware and operating systems. Operating systems are totally separate and mutually exclusive from one another, sitting on one piece of hardware."

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