The parts of the CPU that are not in use can be turned off, so making full use of the vector units can raise the temperature of the CPU a fair bit compared to l

The parts of the CPU that are not in use can be turned off, so making full use of the vector units can raise the temperature of the CPU a fair bit compared to less demanding code. He's also comparing 12 rounds of ChaCha with 12-round AES, which may be fair, but realistically no one uses ChaCha12, they use ChaCha20.