Having fried 1 Arduino Due already, I would like to know whether it's possible to use the USB programming port
and the external power supply at the same time. I know the wiki entry says that the power source is selected automatically - however, is that also true when both power supplies are present?
I also have another little question: When I fried my first Arduino Due, the painting on the Atmel ARM chip evaporated. I can see the same is happening now, although not as fast. Can it be because I've touched the chip, and body oils are at work now? It gets nowhere as hot as my fried chip, but a little lukewarm. Is this normal?
Warning, A transformer type power supply can deliver up to 50% over the rated voltage, depending on how much current it is rated for.
How are you powering your board, what type of supply are you using. If you're using a transformer type supply, it may not be regulated. you need to use a regulated power supply of approximately 9V, to the "power input port" or the "Vin" port. a 12V power supply can be used but it can heat up the regulators. what other items are you trying to power with your due. the do board has a 850 mA limit. Exceeding this limit should not damage the board but even getting close to this limit can cause problems.
do not power the do board using the 5V or 3.3V pins, unless you know exactly what you're doing.
The processor should not get hot if you are using the correct voltage.
if you have used an unregulated power supply, and your processor is getting hot, you may need to replace the due board.
remember only use regulated Power supplies, that are rated for the correct voltage.