The more I think about it, the more boggled my mind gets, as well. I think I can remember a dozen road wins against ranked teams. But in reviewing the record, I find that most of the ones I recall were in tournaments, not on foreign courts....until fairly recently.
The record book doesn't indicate ratings until the 1948 season, so we aren't talking about 100 years, but 67.
From then until Johnny Orr arrived in '80, ISU had 3 wins at ranked teams. Johnny had 2. Floyd had none. Eustachy had 2. Morgan had 2.
My copy of the record book is an old one that doesn't include McDermott or Fred. I know Mac had at least one -- at Kansas State -- and Prohm had one last night, so that would make a total of at least 11 not counting Fred. Is it possible Fred only had 1 road victory over a ranked team? Seems hard to believe. But whether 12 is the right number or not, it's close enough that it doesn't make any difference.
My mind wouldn't boggle until I saw that an average of 1 every 5 seasons is much worse than other P5 teams. But you also have to realize that ISU has only 2 league titles and 4 tournament titles in that time, so the "P" doesn't stand for "Powerhouse."