https://www.cl.cam.ac.uk/~sps32/Z80proj/Z80_traps.pdf https://www.cl.cam.ac.uk/~sps32/Z80proj/Z80_traps.pdf has very high quality imaging of the doping levels,

https://www.cl.cam.ac.uk/~sps32/Z80proj/Z80_traps.pdf https://www.cl.cam.ac.uk/~sps32/Z80proj/Z80_traps.pdf has very high quality imaging of the doping levels, by Sergei Skorobogatov. https://retrocomputing.stackexchange.com/questions/11143/in-the-original-z80-layout-where-are-the-traps-located-and-what-are-their-ef https://retrocomputing.stackexchange.com/questions/11143/in-... references "Zilog oral history" and poses the question, but there isn't a strong answer other than the link to the above. The oral history document referenced is: http://archive.computerhistory.org/resources/access/text/2012/07/102658025-05-01-acc.pdf http://archive.computerhistory.org/resources/access/text/201... . The discussion of traps begins on page 101.