Hector Martin

Nevermind that... Ethernet jacks don't have power pins. Where is this module (that uses so much power that it gets hot) magically powering itself from? Nobody runs PoE out to servers. Did they modify the board design to add power pins too?

Minor nit: power is available for the jack itself since it typically has two LEDs. So if you modified a jack previous to board mounting, you have power. Not enough to need heat dissipation, but enough to run a small chip.

Not a small chip able to MITM 1000BASE-T. You aren't going to get more than 60mW from an LED.

You don't get the power from the led, you draw power from its supply. It only needs to run the logic. You would get further intermitent power from the jack pins. Not backing the Bloomberg piece, just saying it's possible.

I'm talking about the LED supply. 20mA at 3V is the max any indicator LED will be powered at (a lot less these days). LEDs are current limited, so you don't get to draw more. That's 60mW. So no, not possible. Not going to draw any significant power off of the Ethernet pins either

*Maybe* if the LEDs are low side switched *and* the current limiting resistor is on the low side and you wire up yourself between anode and the connector shield you could steal more power, but that's a lot of maybes and assumptions about the board design.

Also, multiple jack parts have access to more led pins, so more power.

16 LEDs are still not enough to run dual 1000BASE-T PHYs + a CPU capable of using them.