It's not because of their temperature. One version of the SH3 (single issue, at 80 MHz) is speced at 260 mW. The SH4 used in the Dreamcast (dual issue at 200 MH

It's not because of their temperature. One version of the SH3 (single issue, at 80 MHz) is speced at 260 mW. The SH4 used in the Dreamcast (dual issue at 200 MHz), seems to be 4W. Hitachi apparently had a trademark on "Cool Engine" for the SuperH (https://www.cpushack.com/CIC/embed/announce/HitachiSH7709.html https://www.cpushack.com/CIC/embed/announce/HitachiSH7709.ht...).