Any CPU will overheat when overclocked, if you don't have a capable enough CPU cooler and good case fan arrangement. The i9's, even more so. Really it depends on WHICH i9 you're talking about, what motherboard you have (Sure as heck don't want to use a cheap motherboard if you're going to overclock on an i7 or i9), how good your CPU cooler is, whether you have sufficient case cooling and what the ambient temperature is in your region or room.