Many creative pros would like to have access to both Mac OS X and Windows XP and Vista from the same computer, whether to have access to the widest range of applications or to test media or Web sites on multiple platforms.

Currently there are two stable ways to do this -- and both require a Mac computer. Either use Apple's beta BootCamp software to install Windows on a separate partition -- which requires you to restart every time you want to switch, essentially running two separate virtual computers out of the same hardware -- or you can use a virtualization tool to run Windows and Mac OS X at the same time.

The effect for the end user of virtualization is similar to using Microsoft's (neé Connectix's) now-defunct Virtual PC for Mac, though with greater performance and stability. We looked at the two leading virtualization systems: Parallels Desktop and VMware Fusion.

Ready for production?

The biggest difference between them right now is that Parallels's product is finished while VMware's Fusion is still in beta testing. In fact, Parallels recently announced the availability of the third beta version of the next release of its software, which includes support for upgrading a virtual Windows XP system to Windows Vista, among other features.

The fact that Fusion is still in beta is rather evident. Several configuration dialogs include the sentence, "This device will be editable in a future release," and there are some minor stability problems.

Performance is another major difference, and it is linked to the fact that Fusion is still in beta. Although the time it takes to install or boot Windows or to run most applications is similar between both Parallels and Fusion, some actions that involve redrawing the screen are slower in Fusion, sometimes resulting in a sluggish feel by comparison.

Running benchmark tests within similarly configured virtual machines under each application reveals dramatic differences in some processor and graphics functions. (Parallels' scores for graphics performance are almost double those of Fusion.) The most likely cause for these differences is explained in a Fusion alert dialog that informs users that it is running in a debug mode that reduces performance and that can't be disabled in the current release.

The finished version of Fusion will tell a fuller tale on the performance front.

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<b>Setup</b>
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Both Parallels Desktop and VMware Fusion are easy to install. Both offer setup assistants that guide users through creating a virtual machine and offer configuration suggestions based on the operating system being installed and the hardware specifications of the Mac.
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Fusion takes advantage of the dual-core processors used in almost all Intel Macs by allowing you designate whether the virtual machine will be able to use one or both cores. This is a nice feature because you can opt to retain the processing power of one core exclusively for Mac OS X and Mac applications, or you can throw all the processing power to the virtual machine.
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Parallels makes setup much easier than Fusion with its "Express Windows OS Installation Mode" that performs the entire install process of either Windows XP or Vista for you. All you need to do is enter your name and Windows activation key. This is both extremely user-friendly and a great-time saving convenience.
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Both products offer a set of tools and specialized drivers for Windows to enhance its performance in a virtual environment. These tools offer things such as a shared folder that can be accessed from Windows and Mac OS X, the ability to respond to the cursor appropriately as you move into or out of the window containing the virtual machine, and enhanced hardware support. Both products also offer a tool for compressing the hard drive image file that serves as the virtual machine’s hard drive.
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The boot process for virtual machines created with either Parallels or Fusion is essentially the same as the boot process for an actual PC. One difference is that Fusion provides you with a virtual BIOS configuration tool that can be used to change boot options such as the order in which the virtual machine searches for a bootable drive. For its part, Parallels manages these features through a virtual machine configuration dialog. Fusion also supports network boot from a Windows PXE server, which Parallels does not.
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Although Parallels boots consistently, Fusion is prone to the occasional unexplained Windows boot failure (generally resolved by simply rebooting the virtual machine).
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Parallels also offers a couple of features that make it more user-friendly than Fusion. One of those is clipboard support, allowing you to copy and paste between Mac and Windows applications. This makes working between the two operating systems much more seamless.

Overall, both Parallels and Fusion rate well in the ease-of-use category -- or will once some of the reliability issues are worked out during Fusion’s development.

Advanced configuration

Parallels offers a much broader set of options for advanced configuration. Fusion currently allows for configuration of shared folders, the use of a single hard drive image file, sound, CD-ROM access (read-only) and some basic network options.

In contrast, Parallels provides the ability to specify more granular virtual hardware information as well as the use of a disk image to mimic the functionality of a floppy drive. Parallels also offers the ability to clone or re-create with a different maximum size the hard drive image of a virtual machine. (Both applications use dynamically expanding hard drive images, but both also require a maximum size be set for the image when it is created.)

Parallels also supports the connection of multiple hard drive images and the use of multiple disk images or physical drives for use as CD/DVD-ROMs, as well as the creation of virtual serial and parallel ports. All of these features make it a more customizable than Fusion to a user or an application’s needs.

Both Parallels and Fusion offer limited choices for how virtual machines handle networking. Both products allow you to choose between using Network Address Translation to share your Mac’s network connection or choosing bridged access to a specific network adapter. Parallels also offers a host-only option that allows the virtual machine to connect to your Mac and any other virtual machines as though they were connected via a network. But it does not allow actual network access.

Neither product supports connection to multiple network cards or networks at this time, though Parallels Desktop 2 promises support for up to five network cards.

USB device access

Both Parallels and Fusion support access to USB devices connected to a computer, though Parallels currently only supports USB 1.1. Parallels gives you the option of having devices be automatically detected and used by the virtual machine or to manually choose the devices that will be used. It appears that this is the how Fusion will ultimately function, but that the capability has not yet been implemented.

Fusion offers access to built-in iSight cameras, Apple's Bluetooth adapter (built-in or USB) and built-in IR ports, which are treated as USB 2.0 devices and are not supported by Parallels.

Overall impressions

Both Parallels Desktop and VMware Fusion are good products. However, it is clear that Fusion still needs some work in terms of its performance and to fully implement its feature set. It also isn’t quite as stable and reliable as Parallels.

All of that is to be expected from a product currently in beta testing, but it does mean that Parallels remains the better option for the time being despite the fact that Fusion offers some features that the commercial release of Parallels doesn’t, such as drag and drop, control over how many processor cores virtual machines can access and full USB 2.0 support.

It is also worth noting that the next release of Parallels is slated to offer at least two of those features -- drag and drop and USB 2.0. It is also slated for several more advances including the ability to use a Boot Camp partition as a Windows boot disk instead of a hard drive image file, greatly enhanced network options and full support for CD/DVD drives (including burn capabilities and access to copy-protected discs). There will also be a new mode called "coherence" that will allow Windows applications to run alongside Mac applications without the need for a separate Windows interface (i.e. Windows applications display right on the Mac desktop and appear in the Dock).

As a result, it seems that for the foreseeable future, VMware will remain a generation behind Parallels.