The VPC's hardware emulation is impressively complete, from the BIOS on down. I ran a hardware-reporting tool on the host system and on three different operating systems running on virtual PCs to compare what was really on the host system to what each of the virtualized operating systems saw.
Table One shows the results: The VPC software thoroughly masks the hardware of the host machine, and provides emulations of fairly common, well-supported hardware that should work with almost any operating system. Not only does this help to make the host machine uncrashable by whatever goes on inside the virtual PC, it also means that the VPC software provides an easy way to create a standardized, widely compatible environment in which to test operating systems and other software. This can remove or reduce one of the biggest headaches in software validation and evaluation.
All virtualization/emulation software exacts a performance penalty: Any time you run two operating systems (or three, or four...) instead of one, you'll get less performance than if you ran each operating system alone.
And, as with any multitasking, the more you want to do at one time, the more horsepower you'll need. Microsoft says the minimum for its VPC software is a 400-MHz PC, but recommends 1-GHz. I found the VPC software slow but usable on an 800-MHz box (the slowest I tested it on), but better on faster systems.
On my primary 3.2-GHz machine, I was able to stream video in background VPC windows with very few dropped frames; and foreground VPCs ran as smoothly as most standard desktop systems I've used. Everything simply felt normal.
In case you think I'm being too generous, check this final screen shot:
(click image for larger view)
With all six operating systems active and running simultaneously, the host system (XP Pro) is using only about 40% of its CPU cycles. XP Home, running on its virtual PC, is using about 18% of the cycles of its virtualized CPU.
Yes, the host machine is a fast one, but being able to run six operating systems simultaneously with 60% of the CPU still available is pretty impressive. Clearly the Virtual PC Software is well made, and makes good use of XP's strong native multitasking.
The Microsoft VPC site lists all the specifics and tech details, so I won't repeat them here; links appear below. Please also remember that this isn't intended as a formal product review but rather as an introduction to what's probably unfamiliar but potentially very useful technology.
As such, please note that there are other VPC tools available, too, including the free, open-source Bochs (pronounced "box") project: By all means, try out different tools.
And when you do, take advantage of the 45-day free trial of Microsoft Virtual PC. It's definitely worth a look. Although Microsoft's Virtual PC isn't free (it's available from many online merchants for $100-$110), and it requires XP to run, I find it a better fit for my needs than the other options I've looked at. (For example, the Bochs site states that it only supports Windows through Win95; I need something that can work with all current Windows.) But as with all things, the final "best" choice is whatever suits you own work style and preferences.
In any case, if you have an interest in running more than one operating system on your system; or if you need to run multiple operating systems for testing, support, or evaluation purposes, a virtual PC solution--and perhaps specifically, the Microsoft Virtual PC--merits a test drive.
As always, your comments, questions, and observations are welcome in the discussion area.