The Microsoft MASM language includes a .K3D directive. The docs are sparse:
Enables assembly of K3D instructions.
Inferring from other directives this seems to be an x86 ISA extension.
I find no instance of the term in the entire Intel Architecture docs. A Google search on intel.com shows 8 results total with nothing useful. A Google search on microsoft.com finds only the MASM docs.
What is the K3D x86 ISA extension? Are there docs available?