There are several virtualisation utilities to run Windows software on a Mac, but Parallels might just be the best
If you need to run Windows software on a Mac, the simplest option is to dual-boot with Apple's Boot Camp utility. But for everyday use, it's more practical to install an OS X virtualisation host such as Parallels Desktop (or its rival, VMware Fusion) to run multiple operating systems concurrently. Both let you hide the Windows desktop and run Mac and Windows applications side by side.
Parallels Desktop 6 brings a few new features that VMware can't match. The big one is a mobile application for the iPhone, iPod Touch and iPad, allowing you to connect to virtual machines over the internet. We tested it on an iPad, and had no problem accessing our Windows installation through a firewall. Once we got the hang of touch controls the OS was responsive and usable, and you can even remotely power-on virtual machines via the mobile app - so long as the host Mac is turned on, of course. It's just a shame you can't access OS X the same way.
There are a few other additions too, including Spotlight support for Windows files and 5.1 surround sound for anyone watching movies or playing games on a virtual PC (although be warned that there's only support for DirectX 9). OS X parental controls are automatically applied to Windows applications, and keyboard shortcuts can be synchronised between operating systems to reduce confusion as you switch between platforms.
The real selling point for version 6, though, is speed. Performance is always an issue with virtualisation, thanks to the overheads of running two operating systems at once, but Parallels claims to give the smoothest Windows-on-OS X experience available.
To put this to the test, we tried it out using mid-range hardware: a 20in iMac with 2GB of RAM and a Core 2 Duo T7300 processor. Running Windows 7 natively in Boot Camp, this hardware achieved an overall score of 0.93 in our benchmarks.
We were pleased to see that Parallels was able to load Windows from our existing Boot Camp partition, although you can also install to a virtual disk file. If you're switching from a PC you can even use the supplied Windows tool to dump the OS and applications to a virtual disk file with a few clicks, and painlessly migrate it into Parallels: we tried a fairly clean Windows 7 installation occupying 30GB on disk, and found it took about an hour.
For our tests, though, we used our existing Windows installation, and accepted the default 768MB of RAM. In full-screen virtual mode, the overall benchmark score fell to 0.68.
It's worth noting that the slowdown was by no means uniform across our tests. Our CPU-based audio encoding test was only 7% slower under Parallels, but tests that opened and closed lots of windows were hit by Parallels' slower graphics performance: the Office test was 20% slower, and Photoshop slowed down by a full 30%, although these applications still felt responsive enough for everyday use.
The worst result was in our 3D rendering test, which was slashed by 47% in Parallels: a brief investigation revealed that, by default, only one core of the Core 2 Duo CPU had been made available to the guest OS, halving the processing power available to multi-threaded applications. Setting Parallels to use both cores restored performance to the expected levels, but left OS X crawling along while 3ds Max hogged the entire CPU.
We then repeated the test in Coherence mode, which hides the Windows screen and presents application windows directly on the OS X desktop. This reduced performance in the more graphical tests by a further 10%, but left us with a still-usable overall benchmark score of 0.64.
Although that's significantly slower than native performance, it's better than VMware Fusion. Its benchmark score in the same test was just 0.61 in full-screen mode. Switching to Unity mode - the VMware equivalent to Parallels' Coherence view - knocked that down to 0.58. The gap isn't huge, but Parallels is clearly ahead.
And if you're tempted to save money with the free, open source VirtualBox package, you'll find a much bigger trade off, in both convenience and performance. VirtualBox won't boot from a real Windows partition, so you can't easily switch between native and virtual Windows as you can with the paid-for packages. Nor is there any equivalent to Coherence or Unity, so running Windows applications means moving back and forth between environments. With a final benchmark score of 0.47, VirtualBox was significantly slower than either of the commercial offerings too.
So for anything more than occasional tinkering it's worth investing in a commercial virtualisation host. And although Parallels costs the same as VMware Fusion, its stronger performance, coupled with niceties such as the mobile application and keyboard harmonisation, give it a small edge. For regular commuters between operating systems, it's worth the money.