the … well, the BIOS could be set so it will … no.
It will need to actively detect the type of cards currently inserted, and listen to (because it’s the host) the power card when the button on the power card is depressed. It will then send some bytes over to tell it to turn on, say, 4 LEDs.
And because of we are actually using USB instead of hard-wiring one, we need to do USB handshake and initialization.
That sound like so much work compared to something that used to live on the battery itself. So you only need maybe 50 extra transistors on the battery controller. Yes, not having it on the battery IC still adds this communication, but this can be done hardware (e.g. below even the BIOS layer and in the power management layer), which might be only a few hundred transistors or maybe 50 lines of code)
Ah. good memories.
