I was compiling OpenCV for the first time on a Raspberry Pi 2 today. This process takes about 2.5 hours and continuously pushes the RPi to the processing limits it's capable of. About 30-40 minutes in, the Pi started beeping. I picked it up and found it was very warm to the touch even through the case it's in, and had even noticeably heated the ESD mat it was sitting on through the case it was in.
I don't recall the exact beep sequence, but as best as I can remember the Pi beeped once, then beeped once again about 20 seconds (approximate) later, then in about another 20 seconds it beeped twice. By that time I had put it on a perch (I used the small box from SparkFun it arrived in) and I pointed a fan towards it. The beeping stopped and within a few minutes after this rearrangement the Pi was barely warm to the touch through the case, if at all.
I did not have any speakers plugged in at the time so I'm certain the beeps came from a part on the RPi board itself, which part I have no idea.
The case I'm using is this one:
which as far as I can tell is the same as this one:
This seems to be the most common case out there at the moment so I would suppose many other RPi users have the same case.
So here are my questions:
1) Has anybody else experienced anything similar?
2) Is there a document somewhere that defines what the beeps (i.e. one beep vs two beeps, beep sequences, etc.) mean specifically? I looked on the raspberrypi.org site and surprisingly could not find such a document. The FAQ section makes a quick mention of temperatures but does not really provide anything concrete and does not mention beep sequences at all.
I suppose I could point a fan at the Pi anytime I'm compiling OpenCV and simply hope this behavior does not occur under any other use cases. I'm curious if anybody has any similar experiences or additional info on this . . .