Microsoft to move graphics outside OS kernel

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Microsoft will move the graphics for its next version of Windows outside of the operating system's kernel to improve reliability, the software giant has told Techworld.

Vista's graphics subsystem, once codenamed Avalon now formally known as the Windows Presentation Foundation, will be pulled out the kernel because many lock-ups are the result of the GUI freezing, Microsoft infrastructure architect Giovanni Marchetti told us exclusively yesterday.

The company has already announced to developers that most drivers, including graphics, will run in user mode - which means that they don't get access to the privileged kernel mode (or Ring 0). At this level, a process can do anything it likes, including overwriting memory that doesn't belong to it. The result of such overwriting by (usually) buggy code is often a system crash. So the move should result in greater reliability, because crashing drivers cause some 89 per cent of system crashes in Windows XP, according to Microsoft. When run in user mode, they won't be able to bring down the entire system.

The shift of the UI into user mode also helps to make the UI hardware independent - and has already allowed Microsoft to release beta code of the UI to provide developers with early experience. IT also helps make it less vulnerable to kernel mode malware that could take the system down or steal data. In broader terms, this makes Windows far more like Linux and Unix - and even the MacOS - where the graphics subsystem is a separate component, rather than being hard-wired into the OS kernel.

Some have noted that this will make it easier to run graphics-rich applications, such as AutoCAD, from terminal servers such as Citrix, as presumably smaller, more compressible primitives will be used, making them faster to transmit over the network. This would mean, for instance, that CPU-intensive operations such as 3D zoom and rotate could be performed locally.

The main downside is the performance penalty to be paid. However, Microsoft originally opened up the kernel mode to the UI and drivers in 1990 with the release of NT4, when hardware was considerably less potent than it is today.

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