No. first it was not an 8080 replacement. Though it may have subbed for 8085 as they were very similar. Two the system had to be configured to run 8088 code(wich is not 8080 or z80 compatable. I had done this to an 8085 system as the signals from the 8088 are the 8085 are very close. The extra plug was likely the remaining 4 address lines (16 bit vs 20 bit addressing). If I had one I could trace it out and regenerate the schematic. Allison