Scoping In On Win4Lin
NeTraverse's Win4Lin Professional is more specific in its scope and application, which makes it well-suited for a single purpose (accessing a few critical Windows applications on occasion) for newcomers and early-adopters migrating from the Windows desktop. Not every situation calls for the full-blown emulation environment that VMware Workstation and Server provide, where these products' resource requirements and operational overhead can be problematic on overloaded or underpowered systems. Unlike the proprietary framework that VMware uses, Win4Lin is built upon free emulation software called QEMU.
QEMU provides a complete emulation environment for x86 architectures. It also remains a work-in-progress and lacks certain capabilities present in more full-featured emulation suites such as Bochs or EMC's VMware. Some of QEMU's shortcomings include incomplete support for Windows OS versions and features (such as Windows XP without service packs or DirectX graphics capability), and a lack of native device drivers for many types of input devices (this means extra overhead when handling multimedia tasks). That said, QEMU is simple, straightforward, and stable enough to emulate Windows on a Linux desktop. It offers both full system emulation (including processor and peripherals) or user-mode emulation for running cross-platform binaries.
There is also a closed-source QEMU accelerator called KQEMU (by the same author) available free of charge to provide QEMU users with near-native speeds for i386 emulation environments. Win4Lin uses both of these components in concert to orchestrate the symphony of software and hardware components available to both the Linux host and Windows guest environments.
The Upshot
Internet capability works right out of the box; no assembly required. Internet Explorer is responsive under emulation and loads the default homepage (the Win4Lin Professional corporate Web site) without hesitation, a considerable luxury for an inexperienced Linux user. This matches the zero-configuration initiative present in many new Windows applications that have graduated from the school of Hands-Free Usability. Overall, installation is quick and painless (failing complications with the KQEMU accelerator module that your authors encountered during a first run through on our demonstration system).
Win4Lin Pro also offers a snapshot option for emulated environments so that no changes need ever be committed to the emulated disk image stored on the host drive. This makes an excellent sandbox against malware, viruses, or general testing of otherwise untrusted executables on a Windows desktop. The default evaluation period has been expanded from 14 days to 30, and supports a more streamlined installation process for a wider variety of Linux distributions than ever before.
Finally, there are three separate guest installation methods:
- image - basic mode; all files, documents, and settings are stored in GUEST.IMG.
- shared - default mode; all files except My Documents folders are placed in GUEST.IMG. These files may then be shared with the Linux host.
- integrated - Windows account settings are kept on the Linux filesystem instead of GUEST.IMG, permitting a sort of "roaming profile"
The Uproar
Certain specialized libraries such as Microsoft's DirectX aren't supported under Win4Lin, so applications written to this framework remain incompatible. Previously, SYSMark2000 had been used to describe the performance differences between native and emulated Windows environments. Later SYSMark versions require DirectX to produce test results. Alas, this rules SYSMark out as a candidate for benchmarking; instead, functional portions of Sandra 2007 are used to illustrate these differences.
There are several known limitations to the Win4Lin Professional environment that vary in relative importance from one set of circumstances to another. A brief summary of some of these limitations appears next. For a complete list, consult the Release Notes stored locally with every installation of Win4Lin Pro in the /opt/win4linpro/docs/Release-Notes.html directory path.
Storage Limitations
Guest disk images (the Windows environment) are limited to a maximum of 64 GB in size, and are restricted to the following OS versions: Windows 2000 prior to SP3, and Windows XP (in either Home and Professional editions) SP1 or later.
Platform Limitations
Windows 2000 updated to SP3, Windows XP without service packs, Windows Recovery and Original Equipment Manufacturer (OEM) versions (factory install CDs) are not supported. Experimentation and experience teach us they are also likely to fail to work properly.
Operational Limitations
The maximum amount of physical RAM that Win4Lin Professional may effectively use is two-thirds of the total usable capacity. This means that for every 256 MB of RAM, Win4Lin cannot exceed more than 160 MB in capacity. While this value can be changed after Windows has been installed, changes to disk space are final once the initial image is created.
