So I am running an Intel Core i5 3570k (at stock speeds)
Installed the stock heatsink.
Using a temp reading tool (RealTemp) is telling me that, at IDLE, any of the given 4 cores are running between 26-36 degrees Celsius.
On load, however, it seems to go off the charts. Playing Guild Wars 2 (on high/ultra settings, I might add, but anyway) brings the average temps up to 70 degrees. Reached Close to 80 during some intense action.
My case currently is quite big and not cluttered, has 2 x 200m fans.
Should i be worried about the temperature of the CPU?
I can't seem to find the acceptable/safe maximum temperature threshold for my CPU anywhere!
Yeah that would be your stock heatsink. Although 70's at full load (although GW2 doesn't bring this CPU to full load, I have both the CPU and the game) aren't actually a problem, I would still recommend buying the Hyper 212 just to take good care of your CPU.
That's extremely hot for a stock CPU....stock cooler should yield temperatures around 20C cooler...can you make sure it's mounted properly? There's a great guide on the Intel Stock CPU cooler on this forum
However, yes, that cooler will significantly reduce temps and will help improve your temperatures.
As others have said, it's extremely likely that the HSF didn't get seated as well as it could have been. In addition to a reseat, you can tweak the core voltage in your BIOS to lower temps. Automatic settings in your BIOS will always run high.