That matmul instruction seemed oddly specific, so I had to google that, and lo and behold, indeed there was such a thing! [0]
Do you remember what kind of speed ups that thing gave you? I wonder if you could play to backport some modern AI algorithms to it and run them at reasonable speeds -- however being a 286 I imagine it'd be quite a challenge.
[0] https://books.google.com/books?id=RD0EAAAAMBAJ&pg=PA89&lpg=P...