Quoted from T-Tommy:I saw this pic with e12 connected to e9.
I created that picture.
I hated the idea of running a long wire from E12 to ground. When I checked the schematics and mapped the U2 ROM address space, tying U2 pin 18 (E12) to address line A11 (E9) made logical sense and looked more elegant.
Low and behold it was already official:
http://www.planetarypinball.com/mm5/Williams/tech/bally_read1st.txt