Graphics Processing in Gaming Laptops
Most modern gaming laptops have two graphics processing units (GPU) onboard. One is the low-powered graphics processor built into the CPU package (also known as an iGPU or IGP). The second is a high-powered AMD or NVIDIA GPU (sometimes referred to as a discrete GPU or dGPU). The reason for the inclusion of both the iGPU and dGPU is flexibility. When gaming, the computer makes use of the dGPU to accelerate the graphics processing. When using less demanding programs, the system switches to the iGPU for efficiency and better battery life. Technically, this type of configuration is called “iGPU passthrough”. Depending on the individual system and configuration you might also see something like hybrid graphics or switchable graphics. Another option is Optimus technology depending on your manufacturer, components, and operating system. In the case of hybrid graphics configurations, to disable the dGPU, the display needs to be physically connected to the integrated graphics. The dGPU basically runs in the background and sends data and images through the iGPU to the display. Sending those frames through the iGPU instead of directly to the display causes two problems. These are increased latency and reduced framerates. Fortunately, there is a better way to connect the display to the dGPU and get switchable graphics, the MUX switch.
What Is a MUX Switch?
A MUX switch connects the iGPU and dGPU to the laptop’s display in a different manner. This allows the dGPU to bypass the iGPU and send frames directly to the display. A MUX switch allows to use the iGPU and dGPU in switchable mode, depending on your needs at the time. A laptop with a MUX is theoretically the best of both worlds. You can use your iGPU for max efficiency or the dGPU to get the best possible performance. So far, MUX switches have been generally implemented by laptop OEMs like ASUS, Lenovo, and Alienware. However other manufacturers might start including this feature into their offerings.
NVIDIA and AMD’s Proprietary MUX Switch Alternatives
AMD and NVIDIA each have their own technologies that accomplish the same thing through similar methods. AMD’s Smart Access Graphics Technology is available for its RX 6000-series and newer graphics, and NVIDIA’s Advanced Optimus is available for its RTX 30-series and newer products. The proprietary solutions developed by AMD and NVIDIA provide the same improvements to framerate and latency as a third-party MUX switch, but each comes with caveats. AMD’s Smart Access Graphics Technology is also only available on laptops with AMD APUs and Radeon GPUs, whereas a third-party MUX switch is vendor-agnostic (meaning it can be used with any combination of AMD, Intel, or NVIDIA silicon).
Is the MUX Switch Better than Switchable Graphics?
As mentioned previously, iGPU passthrough increases latency and reduces framerates. However, you’re unlikely to notice a difference in terms of latency, because the roughly 10% reduction in latency only equates to around 2 ms. Comparatively, total system latency, i.e. the time it takes for the system to process a keyboard or mouse input and show the result of that change on the display, is usually above 30 ms, even on devices with high-refresh-rate displays. Connecting the display directly to the dGPU impacts framerates more dramatically than it impacts latency, so this is where using a MUX switch to bypass the iGPU has the most benefit. On systems with a MUX switch, switching from the iGPU passthrough to the dGPU direct connection usually results in a framerate increase of 10-20%.
Are There Disadvantages to a MUX Switch?
Given that a MUX switch allows operation of the graphics in both hybrid and direct connection configurations, there are few disadvantages. With switchable graphics disabled via the MUX switch, the laptop harnesses its maximum performance at the cost of battery life and efficiency. When switchable graphics are enabled, the laptop can dynamically switch between iGPU graphics and dGPU graphics, allowing for better efficiency. One oddity on some systems is the loss of features when disabling hybrid graphics – for example, our Lenovo Legion 5 drops FreeSync (a technology that controls the refresh rate of a connected monitor) support when hybrid graphics are disabled.
Some Features Might Go Missing
With switchable graphics enabled, the Radeon Software display settings page shows a toggle to enable FreeSync. Using the same laptop, with the NVIDIA GPU controlling the display, there is no option for variable refresh rate option in the sidebar where it should be. Another quirk of MUX-switch-equipped laptops is that in order to make the switch, you must restart the laptop. NVIDIA’s Advanced Optimus does not have this limitation and can switch between switchable graphics to dGPU-only mode on the fly. In the case of an NVIDIA dGPU with a third-party MUX switch, display recording with ShadowPlay is only possible if the NVIDIA GPU is processing the display information, meaning only in supported games, or when running in dGPU-only mode. To record the desktop, you will need to restart the laptop if it’s not already in dGPU-only mode. Some laptops, like the Alienware m15 R5, make you go into the BIOS. There you can switch between dGPU-only and switchable graphics modes. Going into BIOS adds extra hassle to the process and potentially hides the feature from less advanced users. Lenovo’s Vantage software for its Legion laptops allows you to switch graphics in Windows, but shows you a warning that you need to restart to apply the change.
Who Should Buy a Laptop With a MUX Switch?
MUX switches are pretty much only beneficial in gaming applications. Switchable graphics will not affect the performance in professional workflows, like GPU acceleration of video and 3D renders. The only people that should be concerned about a MUX switch are gamers. But not even all gamers should be concerned.
What Games Benefit the Most From a MUX Switch?
A MUX switch mostly affects games that put a lot of strain on the CPU with high framerates. Titles like CS:GO, League of Legends, Paladins, Call of Duty, Battlefield V, and DOTA 2 running at or below 1080p will see the biggest improvement. GPU-limited sightseeing games, like Control, Assassin’s Creed Valhalla, and The Witcher 3 will see less dramatic improvements, especially at higher resolutions. Some games also simply don’t need high FPS. In RTS games like Anno 1800 and Age of Empires IV, for example, a 15% FPS bump would be of little benefit, since framerate doesn’t affect gameplay too dramatically. The same can be said for the aforementioned sightseeing games. Likewise, if you primarily game on an external monitor, you also shouldn’t worry about a MUX switch. HDMI and DisplayPort ports on laptops generally connect directly to the dGPU, removing the iGPU bottleneck.
Check If the Port Connects Directly to dGPU
If you want to verify whether the port connects directly to the dGPU on a laptop in a store or one you already have, you can check this in the NVIDIA control panel: You can also easily check which graphics processor is currently controlling your display using AMD’s Radeon Software: All screenshots by Julian van der Merwe To check whether your laptop has a MUX switch, open the control center software and look for an option to disable hybrid graphics (sometimes also called MSHybrid or NVIDIA Optimus) or enable the dedicated GPU mode (also called Discrete Mode). These options may be buried in a graphics configuration or gaming sub-menu, so it may take some digging. If you don’t see an option to disable the hybrid graphics or enable the dGPU mode in the software suite, you can check in the device’s UEFI or BIOS if there is any mention of switchable graphics, hybrid graphics, or discrete graphics mode. It is not common for laptop manufacturers to bury the MUX switch configuration options in the BIOS. Almost all laptops with a MUX have access to the options via software, but Dell and Alienware gaming laptops are two notable exceptions to this, because they do hide the MUX switch options in the BIOS menus. As a last resort, you can check Reddit, or the manufacturer’s support page to see if anyone else has had a similar question. Many brands like Dell, Eluktronics, and Lenovo have representatives that actively answer questions on forums like r/GamingLaptops, r/dell, r/eluktronics, and r/lenovo.
Laptops With the MUX Switch
ASUS has announced that all of its laptops in 2022 and beyond are designed with either a MUX switch, Advanced Optimus, or Smart Access Graphics. Most of Lenovo’s Legion lineup and many MSI and Eluktronics laptops also feature MUX switches – can you tell the MUX switch became somewhat of a trend in 2021? Nanoreview maintains a comprehensive list of gaming laptops with MUX switches, so if you’re shopping around for a gaming laptop and think you might benefit from a MUX switch, it’s worth checking if the options within your budget are on the list. Image credit: Unsplash and MSI
