I could be wrong but I believe they have a unified address space. There’s dedicated hardware that then owns a given memory range. On an access it will fetch it from the remote location matching that address on demand and store it in real memory in space allocated to it. Presumably it evicts stuff if there’s insufficient memory. Once the memory is brought over either a virtual address range is remapped to point to main memory or the ASIC just has a TLB itself.

This is pure speculation based on seeing the word ASIC in one of the summaries but it seems like it could be reasonable.