NVIDIA Advanced Optimus and MUX Switches Explained
Modern gaming laptops strike an impressive balance between battery life while web browsing, and monstrous performance while gaming – the secret to that is a little technology called NVIDIA Optimus – and the newest version, Advanced Optimus, is a pretty big improvement. Join me as I dive into how this secret sauce works and why you’ll want it on your next laptop!
I’ll start with the problem – how do you get a laptop to have a usable battery life when you’re just writing in word or watching YouTube videos, but also have plenty of horsepower to rip through games at hundreds of frames per second? Well, the method we’ve settled on is you use two graphics cores! The one built into the CPU, the integrated graphics or iGPU, is pretty weak. It has enough power to run the screen, but it isn’t your best choice for gaming. It is, however, pretty efficient, which means it doesn’t use all that much power just to show you cat memes. By contrast, the dedicated GPU, or dGPU, is a power hungry monster, but one that can power through any game you want to throw at it. Because that one sits dormant until it’s needed, you get the benefit of better efficiency when just web browsing, AND more power when gaming.
The problem though is – how do you connect two GPUs to one display AND switch seamlessly between them? Well that’s where NVIDIA Optimus comes in. Basically, the dGPU – your gaming chip – is connected through the iGPU – the low power one – and Optimus will switch which video feed gets shown on the display. For gaming it passes through the dedicated GPU’s output, whereas when just web browsing it turns the dGPU off and only uses the iGPU. The problem with that setup is that your gaming chip has to pass its signal through the integrated GPU which means the iGPU both adds latency, and it has to be running too which saps power that could be going to your gaming chip or your CPU to give you more performance.
So now we get to the new Advanced Optimus feature. The big deal here is that now instead of the dGPU having to pass its frames through the slow iGPU, you now have a fancy switch chip that they both connect to. That means that either can be running – but more importantly, it means the dGPU has a direct path to the screen. It also means the iGPU can be fully switched off when not in use giving more power budget to the gaming chip and your CPU. That fancy switch chip is called a MUX switch – a multiplexer. It’s remarkably simple, it just acts like a two-into-one switch the same as two train tracks that merge into one – but only one is actually “connected” at a time.
One advantage of this feature is that in the NVIDIA control panel if you open the “Manage Display Mode” settings, from there you can control what setting you want to use. Optimus will auto-switch, but if you want to be sure you’re getting the most performance, you can set it to NVIDIA GPU only. There shouldn’t be much (if any) difference on an NVIDIA Advanced Optimus laptop when it comes to gaming performance since the dGPU is only connected to the MUX switch, not through the iGPU. If you’re comparing between two identically specced laptops, one with the standard Optimus and the other with Advanced Optimus – aka a MUX Switch – NVIDIA reckons you’ll get anywhere from 10 to 30% more performance in games. That seems a little optimistic for me, but it’s very difficult to compare two laptops of differing models to properly test that as things like the laptop’s cooling solution plays such a big part in its performance.
Surprisingly though, there is a difference when it comes to latency. Testing in the default mode, OSRTT Pro (available as OSRTT.com by the way), reported the on display latency as just shy of 11ms. That’s pretty slow – on this 165Hz display that means around two frames of latency, with none being lower than one frame. Swap to the “NVIDIA GPU Only” mode and hey presto, you’ve got just 2.95ms of input lag with only one erroneous result taking longer than one frame. That’s really quite significant, so for the best gaming experience I would definitely recommend flicking that setting on before you fire up a game.
In short then, Advanced Optimus uses a MUX switch to change how the two GPUs in modern gaming laptops connect to the screen. Instead of needing to pass through the slower chip, the MUX switch lets the dedicated chip go straight to the display meaning more power is available for the gaming critical components, and you get significantly less latency too. If you can find a laptop listed with either “MUX Switch” or “NVIDIA Advanced Optimus”, you should be good to go.
