Don't forget the joys of core memory. The memory in the CDC machines at UC Berkeley could turn red hot (and even melt) if there was a tight jump-to-self loop. (Core memory is erased by the act of reading, so it has to be re-written after every read - and that used a lot of current and caused a lot of heat.)
On our 7094 the core memory was immersed in cooling oil - and that oil bath sprung a leak. It was a true and honest memory leak.