If it was Furmark I would not make a fuss around it but prime95 is ok for testing. If you get 100c on the CPU something is not ok. Not sure what you mean by run hot all the time? if you use it at 100% yeah it will be hot all the time and when you idle it wont. The problem is not to have a temp of a 100c when you have to use it despite time span while it is 100% utilized.
It seems my posts on prime95 have been missed or overlooked or skimmed by many. The reason people aren't using P95 is because it requires more power than all of their real world loads, and by a large margin. Problem is, none of the programs they're using to check for stability are thoroughly checking for errors. Below is how to overclock with the lowest voltage while ensuring error free operation (which, correct me if I'm wrong here... is what we all want).
Most demanding programs people run (like games) only make CPUs draw 50-70% of the amount of power that prime95 does. A CPU running at 5GHz with 1.3V can run perfectly fine at 80 degrees, but at 95 be throwing errors left and right- 1.34V might be required for proper operation at 95. But then 1.355V is required for temps which are 99 at 1.34, making 1.365V what's actually required. And you're then at 100, thermal throttling.
If none of the real world loads
ever demand power levels as high as P95 small FFT on all cores, 1.35V isn't needed for stability, just 1.3V.
I laid out an easy method to tune to the optimal hypothetical 1.3V using Prime95. Once that's done, the CPU can be power limited so that it never reaches over 80 deg C during operation, and all is good! It will run just as error free in all applications, as if you tested Prime 95 on all cores at once, requiring much less voltage or allowing higher frequencies (take your pick on which you'd like). Caveat: only up to the power levels that normal loads demand of the CPU (which is not a problem because you tuned the power to the real world maximum...)
edit: I put the (very) easy method below for reference. You do with P95 the same as you would if running on all cores. 90-180 minutes coarse adjustments, 30+ hours on the final run
If you don't know already, find out which of your cores are weakest (using prime95 at a lower voltage and clock speed, one that doesn't raise temps above what your real world loads reach). Then, run Prime95 on those cores, adding load to the remaining cores so that your weak cores running Prime95 reach the maximum temperature they do in real-world scenarios. Whatever voltage is required to prevent errors, add an additional 0.02 to 0.03V to ensure stability.
edit: To add heat, google "CPU burn in", in the first result download the 20kB file, each instance is one thread. You can assign them to cores as needed using task manager
edit2: If you're using a high voltage, periodically re-check stability every few months (this goes for any overclock)
