Cpu frequency drops to 0.78 ghz on dell precision m6600

Hello, I've been having this issue for a long time now and it only happens when plugged in, currently I'm using throttlestop to make the ghz back to normal but what it does it doesn't allow me to have good fps in games and I know that it can't be thermal throttling since the 0.78 ghz issue happens when the temps are sitting at around 51-55c. Please help me I'm really stressed