[indigo945]

Parts of DX5 and previous, such as the "retained mode", are missing from current versions of Windows entirely. Much of the remaining implementation is buggy and introduces render artifacts.

Open source projects such as dgVoodoo offer a solution to run old games, by re-implementing old DirectX and Glide on top of current DirectX [1], similar to how Wine runs DX games on Linux on top of OpenGL or Vulkan.

[1]: https://github.com/dege-diosg/dgVoodoo2

[easyThrowaway]

dgVoodoo2 unfortunately is not open source, and its author has stopped regular development (keeping it at small maintenance fixes) some time ago. I can only hope that projects like WineD3D for windows[1] can make up for it in the long term, but we're one breaking Directx update away from going back to the start.

[1]https://fdossena.com/?p=wined3d/index.frag

[int_19h]

Retained mode was deeply unpopular even back when it was supposed to be the flagship API, for good reasons (it was slow as hell), so the games that relied on it for support can literally be counted on both hands.

That aside, the only other old game API that I can think of that's gone for good is DirectPlay, which generally means no multiplayer for games that depend on it as the only option, but otherwise doesn't affect them.