>In article <45ulkp$ppd@post.gsfc.nasa.gov>, > klipsch@ssvs.gsfc.nasa.gov (Colin Klipsch) wrote: >>My question is: which 6502 instructions generate double references? More >>specifically, which instructions will hit the speaker twice instead of >>once, when applied to the speaker I/O addresses? I've looked in >>Leventhal's and Zak's 6502 books, but didn't find this information.