For developers using the SDK, DirectX 1 was a struggle. The API was complex, documentation was sparse, and hardware support was virtually nonexistent. The Runtime layer was designed to sit between the application and the hardware, but video card drivers of the era were often unstable. The concept of the Hardware Abstraction Layer (HAL) was in its infancy, and the Reference Rasterizer (a software emulator) was often the only way to test features.
DirectX 5.0 (1997)Skipping version 4, this release brought major improvements to Direct3D. It introduced the DrawPrimitive API, making it easier for developers to send geometry to the GPU. DirectX 1-8 SDK DDK Runtime
The legacy are primarily used today for retro-development, hardware driver research, or running extremely old Windows software. For developers using the SDK, DirectX 1 was a struggle
This era saw the explosion of the 3D accelerator market (NVIDIA RIVA 128, ATI Rage, 3dfx Voodoo). The relationship between the DDK and the SDK became tighter. Microsoft began releasing "Driver Development Kits" that were specifically tuned to the DirectX Runtime, ensuring that IHVs (Independent Hardware Vendors) could write drivers that handled the DrawPrimitive calls efficiently. The concept of the Hardware Abstraction Layer (HAL)