Virtual 8086 Mode is an operating mode within an Intel CPU that allows it to function as multiple 8086/8088 CPUs. It was developed in 1985 to help multitask DOS “Real Mode” programs alongside 32-bit Windows programs. It divides the computer into multiple address spaces and maintains registers for each of them. This mode has been used in various Windows virtual DOS machine implementations, including the NT virtual DOS machine (NTVDM), as well as OS/2, Unix and Linux virtual DOS machines.
What is Virtual 8086 Mode?
Virtual 8086 Mode is a feature found in Intel CPUs that enables them to function as multiple 8086/8088 CPUs, which were the first x86 chip’s architecture. This mode divides the computer into multiple address spaces and maintains separate registers for each of them, allowing several programs to run simultaneously.
Why was Virtual 8086 Mode developed?
Virtual 8086 Mode was developed to enable multitasking of DOS “Real Mode” programs alongside 32-bit Windows programs. This was important as many businesses continued to rely on DOS applications, which were incompatible with the 32-bit Windows environment. The Virtual 8086 Mode provided a way to run these legacy programs without the need for separate hardware or software.
The Virtual 8086 Mode was introduced with the release of the Intel 386 processor in 1985 and was widely adopted by Windows virtual DOS machine implementations such as the NT Virtual DOS Machine (NTVDM), as well as by OS/2, Unix, and Linux Virtual DOS machines.
How Does Virtual 8086 Mode Work?
Virtual 8086 Mode works by creating multiple virtual machines on a physical CPU. Each virtual machine has its own set of registers, memory, and other resources, making it possible to run multiple programs simultaneously on the same CPU.
When a program is executed in Virtual 8086 Mode, it thinks it is running on an 8086/8088 processor. However, the CPU is actually using Virtual 8086 Mode to create a separate virtual machine for that program. This mode allows the program to access its own memory, CPU registers, and other resources without interfering with other programs running on the same CPU.
The final outcome
Virtual 8086 Mode is a crucial feature that enables complex multitasking on modern CPUs. It allows legacy DOS applications to run alongside modern 32-bit Windows programs and has been widely adopted by many operating systems. With the continued growth of technology, the Virtual 8086 Mode remains an essential feature for businesses relying on legacy applications that are incompatible with modern hardware and software.