Shader Model 6 [upd] -

Furthermore, moving to SM6 required developers to switch their entire toolchain from the old compiler to the new one. For massive game engines like Unreal Engine or Unity, this is a multi-year engineering task involving rewriting shader libraries that have existed for over a decade.

Atomic operations allow a GPU to update a memory location without crashing into another thread trying to update the same spot. Expanding this to 64-bit precision allows developers to use the GPU for complex simulations, path tracing data structures (like BVH traversal), and high-precision physics engines. shader model 6