| dbpprop:abstract
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- In computer science, full virtualization is a virtualization technique used to provide a certain kind of virtual machine environment, namely, one that is a complete simulation of the underlying hardware. In such an environment, any software capable of execution on the raw hardware can be run in the virtual machine and, in particular, any operating systems. Other forms of platform virtualization allow only certain or modified software to run within a virtual machine. The concept of full virtualization is well established in the literature, but it is not always referred to by this specific term; see platform virtualization for terminology. An important example of full virtualization was that provided by the control program of IBM's CP/CMS operating system. It was first demonstrated with IBM's CP-40 research system in 1967, then distributed via open source in CP/CMS in 1967-1972, and re-implemented in IBM's VM family from 1972 to the present. Each CP/CMS user was provided a simulated, stand-alone computer. Each such virtual machine had the complete capabilities of the underlying machine, and (for its user) the virtual machine was indistinguishable from a private system. This simulation was comprehensive, and was based on the Principles of Operation manual for the hardware. It thus included such elements as instruction set, main memory, interrupts, exceptions, and device access. The result was a single machine that could be multiplexed among many users. Full virtualization is only possible given the right combination of hardware and software elements. For example, it was not possible with most of IBM's System/360 series with the exception being the IBM System/360-67; nor was it possible with IBM's early System/370 system until IBM added virtual memory hardware to the System/370 series in 1972. Similarly, full virtualization was not quite possible with the x86 platform until the 2005-2006 addition of the AMD-V and Intel VT extensions. Many platform virtual machines for the x86 platform came very close and claimed full virtualization even prior to the AMD-V and Intel VT additions. Examples include Adeos, Mac-on-Linux, Parallels Desktop for Mac, Parallels Workstation, VMware Workstation, VMware Server (formerly GSX Server), VirtualBox, Win4BSD, and Win4Lin Pro. VMware, for instance, employs a technique called binary translation to automatically modify x86 software on-the-fly to replace instructions that "pierce the virtual machine" with a different, virtual machine safe sequence of instructions; this technique provides the appearance of full virtualization.
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| rdfs:comment
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- In computer science, full virtualization is a virtualization technique used to provide a certain kind of virtual machine environment, namely, one that is a complete simulation of the underlying hardware. In such an environment, any software capable of execution on the raw hardware can be run in the virtual machine and, in particular, any operating systems. Other forms of platform virtualization allow only certain or modified software to run within a virtual machine.
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![[RDF Data]](/statics/sw-cube.png)
