XC2064 was reverse-engineered in 2020:
and I knew about that from this Hackaday article :)
after reading about that I found out that XC2064 was still available from Jameco (not anymore) and I bought a few chips and then found dev-board on eBay:
I was not able to find schematics of it so it looks like 1st activity here would be to reverse and clone this board :)
The only mention of this board on Internet that I found was on Computer History Museum web-site:
where it's called "board from AMD" (and they were not wrong - eventually Xilinx became part of AMD) - it has AM2064 chip onboard that looks fully identical to XC2064...