[M95D]

Hotplug needs support at all levels to work. The connector is just one of them.

In case of PS/2, it needs IRQ12 specifically and it doesn't support shared IRQs like PCI does. If PS/2 is not plugged in at startup, IRQ12 is reassigned by BIOS to PCI or ISA PnP cards, so no matter what OS does, it PS/2 can't work without a reboot.

> PS/2 isn't hot-plug safe even if you preassigned the interrupt (or booted the machine with the keyboard connected and then unplugged and replugged it later), because the pins aren't sequenced, and the circuits aren't designed to tolerate random mating order. If the power and data lines connect before the ground, you can get a CMOS latchup situation in the controller silicon that can only be cleared by total power removal.

It can also be a firmware bug or a momentary brown-out during the connector insertion that glitched the controller, which could happen even if the pins were properly sequenced.