Is it normal that the xbox 360 elite CPU heatsink is cold?

Recently I bought an xbox 360 elite second hand, and decided to apply fresh thermal paste. I noticed that the console is only pushing warm air out the backside from the GPU's heatsink, and only cold air from the CPU's heatsink, even after playing a game for more than an hour. I found this to be strange, and decided to start the console without the plastic casing, so i could directly check if the heatsinks are getting warm.

Turns out that (while in game) the heatsink for the gpu gets warm near immediately, whereas the heatsink for the cpu stays cold. I let the console run for about 5 minutes, and it was still cold. I applied thermal paste the same way for both the GPU dies and CPU die, and am certain that the mounting pressure should be the same for both.

Furthermore, if i feel the metal casing below the GPU and CPU i do feel a bit of warmth coming from the GPU, and no warmth from the CPU.

My question is: is it normal that the heatsink for the CPU stays cold?