So if I understand this correctly... They under-doped certain areas to create depletion mode transistors that any reverse engineer examining the silicon woul

So if I understand this correctly... They under-doped certain areas to create depletion mode transistors that any reverse engineer examining the silicon would expect are regular enhancement mode ones. They strategically placed a handful of these "disguised" transistors, which once incorrectly copied would switch in the opposite manner and wreak havoc on circuit operation. According to one of the designers[1]: I heard from NEC later the copy maker delayed the announcement of Z80 compatible product for about six months. [1] 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-...