Circuits in the CPU and controller chips that enhance the running of multiple operating systems (multiple virtual machines). They deal with functions such as saving and restoring the CPU state upon transitions between the guest OS and the virtual machine monitor (VMM). Available in IBM mainframes for decades as well as in Sun servers and other machines, hardware virtualization came to the huge x86 market in 2004 with Intel's Virtualization Technology (see VT). AMD followed in 2006 with AMD Virtualization (see AMD-V).The First x86 VirtualizationStarting with the Intel 386 in 1985, the x86 CPU family included a Virtual 8086 Mode architecture, which added hardware support for running 16-bit DOS applications in a 32-bit Windows machine. However, this mode did not provide virtual machines for Windows applications (see Virtual 8086 Mode).Virtual Machine vs. Virtual MemoryHardware virtualization and virtual machine are synonymous; however, virtual memory is not. Virtual memory, which is also built into the hardware, deals with extending main memory to disk (see virtual memory). See virtual machine and virtualization.