I put a similar post in the motherboards section when I thought my system was crashing due to high mobo temps. However, after doing a little research it looks like the issue may be my cpu.
I downloaded SpeedFan. Here are my idle temps a couple minutes after startup:
I did a little looking around as to what some of these temps are reading. I have heard that the Temp3 reading is erroneous. I have heard the Temp2 is my CPU. I have looked around at safe operating temps for my CPU and I'm seeing temps below 70c. GPU looks ok I think. Not sure what the first Core reading is. I think the second Core has something to do with my graphics card; they always read the same temp.
So it looks like my CPU is running incredibly hot, and this is the cause of my system shutting off when I play high-performance games.
case fans only decrease the temps by a few degrees at best. The side fan on my case, a bit 120 mm died a few weeks ago and my CPU ran just 4 degrees C higher. So, although it can help, it won't solve the issue
I took a look in the configure section of SpeedFan. It was saying the first Core reading was coming from the AMD K8 chipset. So it looks like my CPU temp was the first Core reading rather than Temp2. Not sure at all what the Temp1-3 readings are.
In BIOS I set an alarm to go off when the CPU hit 70c. However, the SpeedFan temp was close to 80 and no alarm sounded (then off course, my system shut off.) My offset must not be right.