Virtual 8086 mode

So far, most of what has been written applies more or less  equally to the 386 family and the earlier 286 both of which can operate in real or protected mode. However, the 386 has an additional operating mode all of its own – virtual 8086 mode. This allows it to emulate multiple 8086 processors by moving different blocks of extended memory into the first 1MByte to create virtual machines or VMs. Each virtual machine is isolated from the rest and by swapping the blocks of memory very rapidly each one can be given a turn at running. That is virtual 8086 mode makes it look as if there are a number of separate 8086 processors each one capable of running an applications.

Virtual 8086 mode is clearly an ideal way of implementing a multi-tasking system that can run multiple real mode applications in a way that is secure. However, its first common use was for something much simpler in principle, much more complex in practice. While operating in Virtual 8086 mode