A significant change to be introduced in Windows NT™ version 4.0 is the move of GDI and graphics drivers from the Windows NT Win32 subsystem to the Windows NT executive. The benefits of this move include improved graphics performance and memory savings. The move also means that existing Windows NT Win32 display and print drivers will not run on Windows NT 4.0.
This document briefly describes why and how the Windows NT graphics architecture has changed, and why the change makes pre-4.0 drivers incompatible in Release 4.0. It then provides steps for porting Windows NT Win32 subsystem graphics drivers into the Windows NT executive. The explanation sections do not provide a comprehensive look at the new architecture; they provide just enough detail, with a few pros and cons, for background. If you want to skip these sections and begin your port, go to Porting Steps for Graphics Drivers.
Note that your new Windows NT 4.0 graphics driver will not run on pre-4.0 systems.
Note to Video Miniport Driver Writers: Because the video miniports and the video port were already running in the kernel, they did not change at all. All video miniports that worked in Windows NT 3.51 will work in Windows NT 4.0. If you only had a miniport driver that worked with framebuf.dll, or vga.dll, vga256.dll and vga64k.dll, then you do not have to port your driver. These miniport drivers still run with the new versions of their display drivers.