Virtualisation is lining up to be the next big thing, and VMWare is trying to place itself as the most flexible option for running multiple operating systems at the same time. The competition is already well developed. Parallels Desktop has been available almost since the first Intel Macs appeared, and Sun’s VirtualBox has become the go-to app for developers who want a quick check of compatibility between platforms.

At first sight, VMWare’s offering seems slightly more robust and possibly also more full featured. It includes support for a wider range of operating systems (although support for Windows Server 2008 is tagged as experimental). Slightly bizarrely, you can run OS X Server in a virtual machine under OS X Leopard. You can also run various dialects of Linux, as well as Microsoft’s 64-bit operating systems. In fact if you have enough memory you can run them at the same time.

The memory model is flexible. Each OS gets it own independent memory space up to 8GB, from a possible hardware total of 16GB. If you don’t have enough physical RAM, VMWare thrashes to disk in an orgy of swapping. This slows things right down, but it isn’t unexpected or unreasonable. You can even run Windows XP on a 1GB machine. It takes a long time to boot, but it’s perfectly usable once it gets there.

Set up

Setting up Fusion is almost completely painless. There are plenty of options for hardware interfacing and configuration, but the defaults work out of the box, and you can always change them later. Windows can be installed as a new snapshot – which is recommended – or you can convert your old BootCamp partition into a virtual machine with a few quick clicks. Fusion does its best to make this easy. It finds the partition automatically and adds it to the snapshot menu, ready for you to click Play.

The catch is that VMWare’s hardware abstraction model trips the authorisation routine in any application that checks your (virtual) PC’s internals. This means Windows has to be reauthorised, and in our test both Adobe CS3 and Office decided they were running on a different machine and were no longer legal. If you have a hefty collection of Windows apps, you’ll either have to reauthorise many of them, or do without. Note this isn’t a one off problem – every time you switch from booting directly into BootCamp to running virtually under Fusion, you’ll have to reauthorise Windows and some of those other twitchy and nervous applications. This is a very bad thing. While it’s not VMWare’s fault directly, it does make Fusion less than totally convincing as a replacement for BootCamp.

A clean install of Windows solves this problem, and this is how Fusion works best. In fact, you can install different versions for different uses, switching easily between 64-bit versions for audio and video and traditional 32-bit versions for web browsing and email. You can also store backup snapshots before installing new hardware or software, to create an explicit rollback if there are problems.

Virtual reality

Hardware support is good but not quite complete. Mouse control is dealt with by the usual expedient of focus switching. For graphics, VMWare uses its own graphics layer, which means there’s none of the DirectX 10 support that’s built into Vista. Audio and USB support is hit and miss. We tested an external FireWire audio converter with Fusion and got silence. This M-Audio box is usually recognised instantly by Windows, but Fusion didn’t see it. Effectively, Mac drivers seem to take priority, so any hardware you use will need double driver installation - Mac drivers as well as other OS specific drivers. Even then, there’s no guarantee that every hardware option will work.

On the positive side, speed is very good. We tested a graphics application in both native and virtual environments, and there was no obvious speed difference. Fusion seems to be virtualised rather than emulated, which means that it runs as a separate process with full access to processor cycles, and not as a pass-through emulator in the style of Wine. In fact you can assign up to four processors to each running OS.

A couple of other features make Fusion even more useful. File sharing is relatively easy. Unity Mode makes it possible to run virtualised applications as if they were native Mac applications from the OS X desktop, without having to launch the entire virtual OS first. Even though there’s still a start-up delay, this is really quite clever, and a taste of what’s likely to become more common in the future.