This can cause smoke. It depends how the serial card was
designed. But applying voltage to the input ports before
the power supply ports can cause CMOS ICs to latchup.
It depends how the input pads were designed.
And before people grumble about bad designs, its not that
simple. You tend to give up some ESD protection when you
design your CMOS input pads to allow voltage on them before
the power supply voltage. And the pad designs also tend
to be bigger and therefore more costly. Its a tradeoff.
And when the card smokes, it can take the power supply with
it. Personally I wouldn't take the risk.
-- Allen Brown- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.rutgers.edu Please read the FAQ at http://www.tux.org/lkml/