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The GPU applies boost if sees any safe headroom, until one of the limits are reached : temp, power, or volt, and then it will downclock itself to normal rates and then go again if the GPU has work...

I have a similar experience. I bought a second hand 2 year old unit and on the first test the CPU was 92+ deg C while GPU was around 73 deg C. Blimey the CPU was running way too hot I thought.
But...