In modern devices is this why dedicated hardware blocks within the GPU are needed to support ray tracing? Furthermore is there any way to implement ray-tracing on older GPU through some type of software emulation (at I assume a high performance cost)?
My understanding is that the basic hardware accelerator NVIDIA uses is for BVH traversal. However, this is a word-of-mouth thing. I haven't, e.g., looked at their patents or found anyone who has de-capped and reverse-engineered the silicon.
NVIDIA supported (not-quite-real-time) ray-tracing on GPUs for a long time with OptiX. Apparently the RTX APIs look an awful lot like OptiX.