[eropple]

It's been a while, but as I recall, DirectX introduced a hardware abstraction layer from the get-go, but support was pretty spotty for the first few years. DirectX 7 was a pretty big step forward, and coincided with a lot of pretty important 3D features like hardware T&L and vertex buffer allocation. They got there before OpenGL, so the vendors mostly oriented around D3D7 and D3D8, but vendors' implementation was still pretty wonky and bespoke. Shaders hit for D3D9, and you had to pick between HLSL and GLSL, so the gap was widening then but I think the first time you can really describe a rigorous framework for graphics drivers, as opposed to a stack of shims of varying height, would be Windows 2000/XP bringing along XDDM (which then begat WDDM in Vista; WDDM has changed over the years, but is still recognizable in Windows 11).