QUAD-CORE KRYO CPU
More cores isn't always better. Kryo is Qualcomm's first custom-designed 64-bit CPU core that has been engineered expressly to work with the other elements of the SoC, and the Snapdragon 820 has four of these.
They are split into two dual-core clusters that are optimized to operate at different frequencies and power levels. The two cores in the lower power cluster operate up to 1.6GHz and share a 512KB L2 cache, while the other two in the high-performance cluster can go up to 2.2GHz and share a larger 1MB L2 cache.
The benefit of a dual-cluster design like this is that they can split workloads according to how demanding they are. So if the phone was running low-intensity tasks like web browsing or texting, the low-power cluster would fire up. But launch a graphically-intensive game, and the performance-oriented cluster would take over. The overall result of this is lower consumption and better battery life.
Furthermore, Kryo is based on Samsung's efficient 14nm Low Power Plus FinFET process, so overheating issues should be a thing of the past.