getting quite a few HWs on chain one on one of my D3's.

Global Clock is set to 400MHz

Time on: 53 minutes

Chain 1: 25 (Voltage set to 3)
Chain 2: 0 (voltage set to Global LOWEST)
Chain 3: 0 (voltage set to Global LOWEST)

i've bumped the voltage three times now and i'm wondering if perhaps this chain didn't win the lotto.

I've read 10 HW per hour is acceptable. Is that per chain, or a total of all chains per hour?