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Virtual Windows PCs on Macs


My switch to a MacBook Pro has been a learning experience. My major reason for switching was the excellent MacBook Pro keyboard. A prerequisite for the switch was the ability to run Microsoft Windows XP on the MacBook Pro, because I need to run Windows XP every day. My first experience with XP on the MacBook involved booting it using Apple's Boot Camp. I wrote about Boot Camp here noting that it works pretty well. However, Boot Camp is still in beta and the final version will not be released until later this year with OS X Leopard.

Another option for running XP on a MacBook Pro is a virtual machine (VM) application called Parallels Desktop for Mac. One of this application's real pluses is its ability to run under OS X while simulating one or more PC or other OS sessions. You do not need to reboot or press any keys to be able to run Windows XP with Parallels software. If you don't want to run Boot Camp or you need an OS not supported by Boot Camp, Parallels may be just what the tech doctor ordered.

Parallels supports booting and running multiple operating systems at the same time. So you can have many different VMs with operating systems ranging from XP to Linux. Parallels can also boot a Boot Camp partition as a virtual machine. This lets you run applications in a Boot Camp partition in OS X.

What Is A Virtual Machine

Parallels software works by creating a virtual machine that simulates a physical PC in OS X. There is a separation of the physical hardware and the operating system with an abstraction layer, much in the same way Windows XP uses a HAL (Hardware Access Layer) to limit direct access to hardware by programs. The programs talk to Windows and it supplies the access to the hardware. VM programs do this but on a larger scale, creating an abstraction layer inside the host OS that is transparent to the guest OS. The guest PC runs on a VM instead of directly on the native hardware.

This is a screen shot of a Virtual Machine starting. Click the image for larger version.

The major disadvantage of VM systems is that you usually have to share memory, processor, and disk space among the host and guest systems. Both OS X and XP (or any other guest systems) require security updates to keep the systems protected from various attacks. Finally, the guest usually runs without the full power of the host's hardware system, for example lacking multi-processor support. However, many IT professionals have used virtual machines to simulate client systems or environments, to run multiple servers on a single piece of hardware, and as test beds for deploying new applications. VM systems are very useful; I have used them for years. Now to see how Parallels under OS X works.

This is a screen shot of the first boot of a Virtual Machine. Click the image for larger version.

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