Emulators & Virtualizers

One source of compatibility problems with older programs and games is that APIs change as newer Operating Systems are released. APIs, or Application Programming Interface, is how a program communicates to the Operating System, which in turn communicates with the hardware via drivers. As the APIs evolve, the old games are increasingly unable to talk fluently with the OS, to the point that they no longer speak the same language. This is why we sometimes have to run the old games in the OS that they were written for.

Setting up a dual boot is one way to address this, but as newer hardware is often not supported by older OSs, this is not always practical or even possible. No driver support or lack of available required memory addresses are some of the reasons why. This is where emulators and virtualizers come in.

Emulators, such as DOSBox, creates a mathematical model (in the form of a software program) that emulates ALL of the hardware, including the CPU. Because of this, the overhead of running an emulator can be rather high, but potentially perfectly emulate the ideal environment for your old program or game.

Virtualization is similar to emulation, but only emulates part of the PC. For some functions, such as the CPU, it uses some of the host machine's real hardware. Because of this, a virtualizer will not shield you from speed issues or other incompatibilities, but will allow you to use a different OS than that of the host PC. With a virtualizer you create a virtual machine that you can run your old program in, from within the host machine.

Virtualizer Pluses:

Because they do not do full emulation, the overhead can be lower than that of an emulator, though this is somewhat offset by the overhead of a second OS.
They fully support 32 bit Operating Systems and in some cases, even 64 bit.
You can install almost any OS that was designed for the architecture of the virtual machine.

Virtualizer Caveats:

Unlike DOSBox, you will also need to own and install the desired Operating System in your virtual machine.
You will not be shielded from all hardware incompatibility issues.
Audio hardware emulation is no where as good as that of DOSBox.
Development goals of these virtualizers are generalized, whereas DOSBox's development goals are old game compatibility. As such, DOSBox can emulate a wider range hardware than the above virtualizers need to or can.
Direct3D is not available on most virtual machines.

Conclusions

DOSBox should still be your first solution for DOS and Win 3x games. For Win 9x games, try to run them natively in Windows with "Compatibility Mode" and in some cases various patches, etc. For some games, a virtualizer may be your only answer. Though I view it as a solution of last resort, it is a utility that belongs in every classic gamer's tool kit.

Final notes: There are other uses for VPC. I have successfully used VPC to install games that will not install in XP, but will run in XP. Install it in VPC, transfer the files to the host machine and find any registry entries, "Start Menu" items that need to be made or system files copied, etc. You can also use it to try things that think might be risky before you install it on your real OS. You can easily keep a backup copy of any virtual machine.

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