IBM THINKPAD 760C/CD (9546) - Manual (Page 290)

The PS2 HIBernation command is set in the
ThinkPad Features program.
Event that causes the computer to exit hibernation mode.
The power-on switch is operated.
When power is turned on, the hibernation history in the
boot record on the hard disk is recognized and system
status is restored from the hard disk to resume operation.
278 IBM Mobile Systems - ThinkPad HMM Volume 3