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Kernel-Mode Print Drivers: Gone the Way of the Dinosaur
If you have been around since the days of Windows NT, then you are probably all too familiar with Kernel-mode Print Drivers and the devastating effect that problems with those drivers can have on system stability. In the majority of environments, these kernel-mode drivers have been supplanted by user-mode drivers. However, there are still many environments where applications use legacy printers that rely on kernel-mode drivers. So what is the future for those environments and drivers?If you think about print drivers in the simplest terms, there are two parts to all Win32 Print Drivers - one part which performs the rendering of the print job, and one part which is provides configuration options for the user. Although the configuration piece has always run in user-mode and normally in the context of the user requesting the printing, the rendering part has moved between user mode and kernel mode. In Windows NT4, GDI drivers for both printing and video ran in the Kernel space for performance reasons - namely that the video drivers suffered a performance hit when switching back and forth between user and kernel mode. However, although the video drivers benefited from the move to the Kernel space, printer drivers did not. If a printer driver experienced an error (such as a crash), the entire machine would bugcheck which resulted in stability and availability issues.(continue at source)