What is a MUX Switch in a laptop?
A MUX Switch lets you switch between different video card modes. For example, some laptops have the ability to use both AMD and NVIDIA graphics cards. However, if more than one of these were plugged in, your system might not boot up (or your screen might freeze randomly). This is where the multiplexer comes in. It allows you to switch between the cards, like a toggle.
A MUX switch is a double throw, triple pole toggle switch that allows the user to select whether one of two or more video sources is connected to and displayed on the monitor. So when you want to use an external video card, for example, you turn it on, and when not, turn it off.
The MUX switches in most laptops are manually controlled, meaning you have to change the settings yourself. Some laptops come with automatic switching, which switches between cards based on what programs you are running at the time. This saves battery life and allows you to use either card without switching it manually.
So there is little internal circuitry that tells the laptop when to switch over, so be careful when handling the internal components. The MUX switch can be either a push button or toggle switch that selects between two or more separate video card inputs and displays the selected input on the monitor.