another boot, AC plugged in, went off to get coffee, came back and saw that it 'woke up' after the first pause:
[ 3.237431] hub 2-0:1.0: 2 ports detected [ 174.074748] Clocksource tsc unstable (delta = 4398044839120 ns)
but then paused. I unplugged AC, it unpaused, then paused, plugged in AC, it continued to boot, no pause.
another boot, AC plugged in, went off to get coffee, came back and saw that it 'woke up' after the first pause:
[ 3.237431] hub 2-0:1.0: 2 ports detected
[ 174.074748] Clocksource tsc unstable (delta = 4398044839120 ns)
but then paused. I unplugged AC, it unpaused, then paused, plugged in AC, it continued to boot, no pause.