Fascinating. The old designers were amazingly creative with their limited resources. The decoding logic for the 8087 is… ahem… interesting with how it interacts with the 8086. Amazing that it works at all. Would be interesting to see the actual microcode source and how some of the algorithms are implemented.

I always enjoy your write ups, @kens. I was doing hardware design in the late 1980s/early 1990s, and so this takes me back.