Why is my motherboard's CPU temperature inconsistent with the individual core temperatures?

This image demonstrates what I'm talking about:

The motherboard's CPU temperature is in green. The individual cores' temperatures are in red.

I've tested the temperatures in three different scenarios:

• Idle: All cores <5% utilization. Core temperatures are around 70C, while CPU is around 55-60C. Frequency stays around 2600 Mhz.


• Gaming: Three of six cores around 50% utilization, remaining three <10%. Core temperatures gradually increase to 90C. CPU temperature gradually decreases to 40C. Frequency is gradually reduced to 1200 Mhz. Pictured above.


• Stressed: Using Intel's diagnostic tool to stress the CPU; all cores near 100% utilization. All cores are over 90C, while CPU is at 80C (I believe the tool limits itself if it goes above 80C). I can't monitor frequency during this.

Why are the two readings so different? Also, why does the motherboard's reading decrease while gaming, even though the Core readings are almost as high as they are during the stress test?