There were two experiments that caught my memory back then. The first was them trying to understand why the ARM chip they had on a test board was working, desp

There were two experiments that caught my memory back then. The first was them trying to understand why the ARM chip they had on a test board was working, despite the fact that the power supply wasn't plugged in. It transpired that there was leakage currents from the keyboard which ended up giving the CPU enough power. (Discussed in a Computerphile YouTube video on the origins of ARM.) The other was a demo of showing an ARM chip being powered off a thermocouple of the waste heat from a 286 (or maybe 386 ... either way an old Intel CPU)