Writing graphics card drivers in the 1990s was a nightmare, and often the most complex part of an operating system, particularly ones that supported protected m

Writing graphics card drivers in the 1990s was a nightmare, and often the most complex part of an operating system, particularly ones that supported protected mode and virtual DOS machines. Windows/386's graphics card driver was so integrated with the protected-mode kernel that it had an entirely different kernel for each graphics card. It came out of the box with support for CGA and EGA, and a later version added Herculues, VGA, and 8514/A. That was it. By Windows 3.0, it had a more modular architecture - but this made the drivers even harder to write. A driver that would run in user space had to be written in 16-bit assembly or C. And then a secondary driver that would run in kernel space had to be written in 32-bit assembler, and that driver had to completely virtualise the device for DOS apps (and also had to provide a virtual device the aforementioned 16-bit driver could use). Drivers for OS/2 got even more complex: the above 16-bit Windows driver was still needed. Plus a 32-bit protected-mode driver for OS/2 apps. Plus a "base" 16-bit driver for character mode when the system was booting, although most cards could use the generic VGA or SVGA driver for that. Plus the 32-bit virtualisation driver for DOS apps. Plus a specialised 16-bit Windows driver that would share the display with the 32-bit protected-mode driver so that both Windows and OS/2 apps could be on the display at the same time. XFree86 was the usual way to support graphics cards on Linux, alongside very simple kernel-based drivers for character support - or more complex drivers for framebuffer support. If you wanted to run XFree86 on OS/2, you had to have a separate executable (just like Linux) for the specific graphics driver. So an OS/2 machine could end up having this many graphics drivers: - Base video driver, e.g. BVHSVGA - 16-bit Windows full screen driver - 16-bit Windows seamless driver - 32-bit OS/2 Presentation Manager driver - 32-bit virtualisation driver - 32-bit XFree86 driver NT would be yet another driver, although at least on NT it was just a single kernel space driver, and Windows 95 yet another. Windows 95 needed the same virtualisation driver as prior versions. NT didn't typically provide that, but NT was also notorious for poor support for DOS games because of that. Some vendors actually supported all of these. You'd get a couple disks with a graphics card for GEM, DOS (VESA), OS/2 (16-bit and 32-bit), Windows 2.x, 3.x, NT 3.x, and even SCO Unix. The workload to write all these drivers was insane.