the processor thinks and the hard drive stores memory, ostensibly they're both part of the brain. so what's the heart? power supply? not a very romantic interpretation, is it?
why is the heart the part with which you're supposed to love, anyway? were it not for that poetic analogy, simply drawing parallels with the power supply would feel more natural, but it doesn't. what makes a robot love then?
someone from my discord suggested that it could be the northbridge -- arguably it's what's responsible for all interactions with the outside world, connecting expansions directly to the CPU bus