What is the normal fan speed on Mac computers I have noticed that fan speed on my Mac is 499 rpm. Now this is a computer with installed OSX El Capitan, Xcode 8.2.1... I have noticed this when Xcode got crashed few weeks ago (the information was provided in Xcode crash log). Now, today, when it crashed again, I have noticed the same fan speed, which is 499...That is a bit odd I must say, because rpm are very low, and I got same number twice.

I wonder is this accurate info actually and what is the normal fan speed for MacPro3,1?
There is no "normal" speed for a fan in a computer.  The fan spins at a speed necessary to keep the CPU temp in the "normal operating range."1

For your particular Mac, the  maximum operating temperature is about 82°C (180°F).  However, keep in mind that this does not factor in other components like heat from drives, adapters, etc. which may also go into calculating when a fan is engaged.



1 See section 5 in Intel® Xeon® Processor E5-2400 Product Family Thermal/Mechanical Design Guide May 2012