Z80 mystery solved!

Z80 mystery solved!  Many moons ago, long before my beard turned gray and my hair fell out, I made extensive use of Z80 microcomputers in systems I designed.  I probably built 25 or 30 different systems using that part, so I got to be very familiar with it.  The pinout of the Z80 DIP had one striking oddity: the eight data pins were out-of-order, as if the chip makers had scrambled them.  This was in marked contrast to the sixteen address pins, where were in a nice, neat, orderly sequence that wrapped around the top of the package.  Why would this be?  Why not have all the data pins in order?

Well, now we know!  It took almost 40 years to figure it out...