オリジナル投稿者： Rany ,
This model of screen has a small thermal sensor with cable that is attached on the screen. [br] If you turn the old screen, look at the back/top. You will see a small board that has two cables plugged in. One of those usually connects to the main mother board (the larger cable), the other one (the narrower and shorter cable) goes to a tiny piece of circuitry which is actually the thermal sensor. [br] With that sensor unplugged (if you left it on the old screen and did not transfer it to the new screen), the fans will ramp up to the max speed, and the iMac will interpret it as something is overheating and will consequently slow down. You can double check this by installing a temperature monitor like Aidan suggested. It should say that the LCD thermal sensor is bad/missing or giving a high temp signal.