The MUX switch is a feature found on newer gaming laptops that toggles between discrete and integrated graphics. The feature itself isn't new, so what is a MUX switch actually for?
The bottleneck
Most modern gaming laptops have two graphics processors, an iGPU and a dGPU. The iGPU (integrated GPU) is the graphics core built into the CPU, while the dGPU (discrete GPU) is a separate graphics chip. To balance performance and battery life, manufacturers let the system switch between the two using NVIDIA Optimus (also known as MSHybrid) and AMD Switchable Graphics.
NVIDIA Optimus and AMD Switchable Graphics can give gamers the power of a discrete GPU when they play and good battery life during everyday tasks, but neither technology is perfect. When Optimus activates the dGPU for heavy rendering work such as games, the frames the dGPU renders still have to "borrow" a path through the iGPU. Because the iGPU is less powerful and has less bandwidth, a bottleneck forms at that point, causing a drop in performance and added latency.
To solve this problem, engineers developed the MUX switch, short for multiplexer switch.
MUX switch
A MUX switch works much like Optimus or Switchable Graphics in that it toggles between the iGPU and dGPU, but with one key difference: it lets all graphics data flow straight from the dGPU to the laptop display without borrowing a path through the iGPU. Naturally, this affects the laptop's battery life, but in exchange it boosts performance and cuts latency in games. At its core, a MUX switch is a physical microchip on the motherboard that can switch the display connection between the dGPU and the screen, and users can control it through software.
The drawback of a MUX switch, being a microchip, is that it can't be added through a software update the way Optimus or Switchable Graphics can. In addition, every time you enable or disable dGPU mode with the MUX switch, you have to restart the system. That's a bit of a hassle, even though the wait is only about ten seconds. According to ASUS, bypassing the iGPU adds roughly 9% to frame rates across games, and in Rainbow Six Siege and Shadow of the Tomb Raider the difference can reach 30%.
Because a MUX switch creates a direct connection from the dGPU to the display, it does more than raise performance. It also enables features the dGPU supports, such as NVIDIA G-SYNC. Optimus is also an NVIDIA technology, yet it doesn't support G-SYNC even though the dGPU itself has the feature.
How can you tell whether a laptop has a MUX switch?
Oddly enough, most manufacturers don't advertise the MUX switch much in their marketing, and they don't list it in the specifications either. For the most accurate answer, ask the retailer, the distributor, or the manufacturer directly.
Gaming laptops usually ship with a control app from each brand: MSI has Dragon Center, ASUS has Armoury Crate, HP has Omen Gaming Hub, and Lenovo has Lenovo Vantage. Look in the app for your laptop's brand under GPU switch, GPU working mode, or something similar. If there's an option such as Discrete Graphics or dGPU Mode, and the system asks you to restart when you enable it, your laptop has a MUX switch. Digging through the BIOS/UEFI is another way to check.
"Cheating" your way to MUX switch behavior
If your laptop doesn't have a multiplexer switch, you can still try to get the same effect with a workaround. The video outputs for external displays (DisplayPort, HDMI) on a laptop are typically wired directly to the dGPU, not through the iGPU. If you use only an external monitor, the system has no choice but to send the signal straight from the dGPU to the screen, since the iGPU's output is the laptop display. The advantage of this workaround is that you don't need to restart. You just set the system to output only to the external monitor and turn off the built-in display, and that's it.
Testing
The gaming laptop I used to test MUX switch performance is the Legion 5 Pro, configured as follows:
- CPU: Intel Core i7-12700H
- RAM: 16 GB
- iGPU: Intel Iris Xe
- dGPU: NVIDIA GeForce RTX 3070 Ti 8 GB
- OS: Windows 11 Home
The tests I ran were:
- Horizon: Zero Dawn - Original preset at 1920 x 1080, Vsync off.
- Shadow of the Tomb Raider - 1920 x 1080, DLSS off, Vsync off.
- Path of Exile: Archnemesis - 1920 x 1080 with all effects at the lowest setting. This MMORPG has been around for quite a while, but its effects are very demanding when maxed out, especially with the build I tested, a CWDT build in which the character automatically casts about 5 times per second, 7 skills each time, with a huge number of projectiles. I only turned on the skills and ran around the hideout to keep the conditions the same for every test. Running maps wouldn't let me control the number of monsters or their skills and effects, which would produce inaccurate differences.
- Final Fantasy XIV: Endwalker - all defaults, Full HD resolution.
- 3DMark Professional Edition - Time Spy, Ray tracing and DLSS feature at a target resolution of 2560 x 1440, Performance mode.
- Unigine Superposition - 1080p Medium.
The results show that there is a difference, but it isn't consistent. Using the dGPU directly through the MUX switch brought about a 1.6% difference in Unigine score (19,009 vs. 18,710), and average frame rate rose from 99.28 fps to 103.72 fps. Time Spy showed a very small difference in Graphics score (10,773 vs. 10,750). In the 3DMark DLSS feature test the difference was imperceptible (DLSS on: 72.80 fps vs. 72.60 fps), and with DLSS off the dGPU mode was even slightly lower (30.47 fps vs. 30.52 fps). Ray tracing was similar, at 27.75 fps with the MUX switch on and 27.66 fps with automatic switching.
In games, Shadow of the Tomb Raider gave equal results, averaging 140 fps in both modes, while Horizon: Zero Dawn showed a gap of only 6 fps on average (127 fps vs. 121 fps). Path of Exile probably showed the most noticeable difference, measured with FRAPS: in automatic switching mode the game averaged 139.76 fps, but with the dGPU alone it reached 173.64 fps. Final Fantasy XIV's benchmark scored dGPU mode 2122 points higher than hybrid mode (20805 vs. 18683), and during play the frame rate also differed, though only slightly.
Conclusion
At this point, I can conclude that there is a reason most manufacturers quietly include a MUX switch without advertising it loudly or putting it on the spec sheet. The performance difference with and without a MUX switch is almost impossible to notice, while battery life takes a considerable hit. The performance loss and added latency from the dGPU signal "hitching a ride" on the iGPU's lane do exist, but they really aren't worth trading away battery life or putting up with a restart every time you switch with the MUX switch. Of course, you're free to use the feature and ignore all of the above, if "I just like it" is reason enough. Or, if you have the time, try turning the MUX switch on and off in the games you play most, measure or feel the difference, and if it's worth a few inconveniences, go ahead and use it.
That said, as mentioned at the start, a MUX switch isn't only about performance. It also unlocks features the dGPU has natively but that are disabled when the signal passes through the iGPU, G-SYNC being the prime example. I tried using the MUX switch to switch to dGPU-only mode, and once in the operating system, the NVIDIA Control Panel offered many more options, similar to using a discrete card on a desktop (3D Settings, Display, Video), including G-SYNC. When I switched back to automatic mode (Optimus), those options were hidden, leaving only 3D Settings.
