The latest AAA games require more graphics horsepower for an immersive experience than the typical ultraportable laptop can provide. Dedicated gamers will often buy a beefy gaming laptop that can run such titles to their satisfaction, or reserve gameplay for their desktop PCs at home. A third option is to connect an external GPU like the Asus ROG XG Mobile to an ultraportable laptop. The XG Mobile is one of the better external GPU (eGPU) concepts we’ve seen, but it’s still an imperfect and expensive solution, with the XG Mobile and bundled ROG Flow X13 laptop starting at $2,999 and offering decent but hardly noteworthy performance. Most gamers will be better off with sticking with a beefier gaming laptop.
Portable and Flexible Gaming Performance
Traditional eGPUs like the Razer Core X Chroma or Lenovo Legion BoostStation seek to offer a blend of portability and performance. They’re not portable themselves—often they’re large boxes about the size of a mini desktop PC that stay at home on your desk and connect to a laptop via a Thunderbolt port. But they allow you to use an ultraportable laptop when you’re on the road with no use for a beefy gaming rig, and connect to the eGPU when you get home and want to indulge in a bit of fragging with silkier frame rates than your laptop could manage on its own. By contrast, the XG Mobile is, as its name suggests, designed to be carried with the Flow X13 laptop when you’re out and about. It measures 1.2 by 15.5 by 20.8 inches (HWD) and weighs 2.2 pounds, dramatically smaller and lighter than the 7-inch-tall Core X Chroma. Instead of a Thunderbolt connection, it features a proprietary Asus locking plug that is currently compatible only with the ROG Flow X13. As a result, the laptop and XG Mobile are currently available exclusively as a bundle, though Asus does plan to sell them separately starting later this year.
Limiting the XG Mobile to working with a single laptop makes it significantly less flexible than most other eGPUs. And the proprietary plug means you can’t try to use it with an unsupported laptop even if you want to. Depending on your gaming needs, however, its portability might make up for this lack of flexibility. So might the added benefits of the proprietary connection. The XG Mobile’s proprietary interface is based on the PCI Express Gen 3 standard, with eight lanes of throughput. Asus says this eliminates any potential performance bottlenecks and allows the graphics card inside to perform as well as it would if it were inside the laptop.
The Core X Chroma and other similar Thunderbolt eGPUs do suffer from significant bottlenecks related to the Thunderbolt connection’s overhead, in some cases. We found that the Core X Chroma equipped with a GeForce RTX 2080 Ti performs worse than a desktop PC with a built-in GeForce RTX 2060.
Mobile (Not Desktop) RTX Inside
While the XG Mobile may not suffer from Thunderbolt bottlenecks, its performance is still lower than that of a larger eGPU equipped with a desktop graphics card. The XG Mobile’s small size limits it to the laptop version of Nvidia’s latest RTX 3080 GPU. It’s an impressive processor, but as you’ll see in the performance section below, it doesn’t quite match up to the equivalent RTX chips built into a laptop, let alone the desktop version.
Using the latest RTX 3080 also means that the XG Mobile is subject to the increased variation in maximum performance of RTX 3000-series laptop processors. The version Asus uses here is clocked to 1,810MHz and uses 150 watts of power. These specs may not match those of other laptops with built-in RTX 3080 processors.
Besides eliminating bottlenecks, one advantage of the proprietary connector is that it also supports data throughput for the XG Mobile’s built-in expansion ports. On the back of the device, you’ll find four USB Type-A ports, an SD card reader, a gigabit Ethernet jack, an HDMI 2.0a output, and a DisplayPort 1.4 jack. This means that not only can the eGPU boost your graphics output, but it can also serve as a hub to connect your laptop to external displays and other peripherals with ease. The Flow X13 and XG Mobile together can power up to four monitors—two connected to the XG Mobile, and two connected via the laptop’s HDMI and USB-C ports.
With its 280 watts of total power, the XG Mobile can also power and charge the Flow X13. If you’re carrying both around with you, this means you won’t need the laptop’s AC adapter. And since the XG Mobile has no power brick of its own (its AC adapter is built-in), that further simplifies your cable collection.
You won’t find any adjustable RGB lights on the XG Mobile like you will on the Core X Chroma, but that doesn’t mean it’s devoid of gaming flair entirely. There’s the obligatory Republic of Gamers (ROG) logo embossed on the ribbed black metal top, and even a red LED that shines through the thermal grille on the bottom of the device. You’ll only see it in a dark room, but the faint glow should reassure people who don’t want their XG Mobile to just look like an oversize black power brick.
A Cinch to Set Up
The XG Mobile’s easy connection process stands with its portability and I/O offering as one of its best features. Compared with the often-arduous process of cajoling your PC to recognize an eGPU over a Thunderbolt 3 connection, the XG Mobile is a cinch.
You first remove the cover on the proprietary port on the left side of the Flow X13 laptop. This port can also serve as a USB-C connector if you’re not using the XG Mobile. Do the same for the protective cover on the XG Mobile’s plug. Unfortunately, the covers are not tethered, so you’ll have to find a safe place to keep them.
As soon as you connect the XG Mobile to the Flow X13, an LED on the plug will shine white. Then, slide the switch on the top of the plug to the locked position, which physically prevents you from unplugging it. The LED will change to red, and a software prompt will show on the laptop’s screen asking if you want to switch to the XG Mobile. Click OK, wait a few seconds for the progress bar to complete, and you’re done. In my testing, the RTX 3080 automatically displayed as a display adapter in Windows Device Manager and was recognized in games.
To disconnect the XG Mobile, you’ll need to reopen the software utility, whose icon can be found in the Windows Notification Center. Click OK to deactivate the device, and once the LED changes back to its white color, you can unlock the plug and remove it by squeezing the two buttons on either side.
Asus notes that the XG Mobile is designed to be connected or disconnected only with the Flow X13 laptop booted up. If you shut down the system with the eGPU connected and then disconnect it while it’s off, you’ll get an error message when you turn it on next.
Acceptable But Uninspiring Performance
The XG Mobile will transform the Flow X13 laptop from a machine that offers the bare minimum performance required for smooth gameplay on demanding titles to one that can comfortably churn out frame rates in excess of 60 frames per second (fps) at a full HD resolution (1,920 by 1,080 pixels). But it doesn’t offer meaningfully better performance than beefier gaming laptops equipped with ostensibly less-capable RTX 3070 graphics processors. In fact, in many cases, it offers worse performance than these laptops. And it can’t hold a candle to the performance you can expect from a desktop-class RTX 3080 GPU.
For a closer look at how well the XG Mobile performs, I compared its results on our gaming benchmark tests with those of the Flow X13 on its own. I also threw in a few other RTX-based laptops and the RTX 3080 Founders Edition desktop card. You can see the specs of all of the laptops in the charts below:
Our first test, 3DMark, measures relative graphics muscle by rendering sequences of highly detailed, gaming-style 3D graphics that emphasize particles and lighting. We run two different 3DMark subtests, Sky Diver and Fire Strike, which are suited to different types of systems. Both are DirectX 11 benchmarks, but Sky Diver is more suited to laptops and midrange PCs, while Fire Strike is more demanding and made for high-end PCs to strut their stuff. The results are proprietary scores.
The addition of the XG Mobile more than doubles the Fire Strike score of the Flow X13 on its own. The XG Mobile also leapfrogs the AMD Radeon RX-based MSI Alpha 15 and the Lenovo Legion 7i, equipped with a previous-generation RTX 2080 Super. But the Fire Strike score of around 18,000 is still lower than that of the new Alienware m15 R4, which uses an RTX 3070 that is one step down from the RTX 3080.
Next up is another synthetic graphics test, this time from Unigine Corp. Like 3DMark, the Superposition test renders and pans through a detailed 3D scene and measures how the system copes. In this case, it’s rendered in the company’s eponymous Unigine engine, offering a different 3D workload scenario than 3DMark, and a second opinion on the machine’s graphical prowess.
The Superposition results mirror the 3DMark ones. While the improvement at 1080p over the laptop without the XG Mobile is impressive, it’s still not quite as good as the RTX 3070-equipped Alienware.
The synthetic tests above are helpful for measuring general 3D aptitude, but it’s hard to beat full retail video games for judging gaming performance. Far Cry 5 and Rise of the Tomb Raider are both modern, high-fidelity titles with built-in benchmarks that illustrate how a system handles real-world video games at various settings. These are run on both the moderate and maximum graphics quality presets (Normal and Ultra for Far Cry 5, Medium and Very High for Rise of the Tomb Raider) at native resolution to judge performance for a given system. The results are also provided in frames per second. Far Cry 5 is DirectX 11 based, while Rise of the Tomb Raider can be flipped to DX12, which we do for the benchmark.
The Far Cry 5 and Rise of the Tomb Raider results clearly show that the XG Mobile transforms the Flow X13 from an entry-level machine (with performance not far above the 30fps floor we consider the minimum for smooth gameplay) into one that can deliver more than the 60fps we consider the ideal. However, on both titles, the XG Mobile’s performance is far lower than that of the RTX 3070-equipped Alienware. It is also lower than even the Radeon RX 5600M-equipped MSI Alpha 15 on these two games.
This situation is clear evidence that the XG Mobile-Flow X13 bundle is an expensive and not-quite-as-capable alternative to a beefier gaming laptop. Sure, it will get you performance when you need it and portability that the other laptops shown here can’t match, but it comes at a high cost, both in terms of money and potential frame rates. For people who plan to game at 1080p, this could be an acceptable tradeoff. But note that the version of the Flow X13 with a 1080p screen also has a 120Hz refresh rate, which means it is capable of displaying more than the about-80fps that the XG Mobile can manage on Far Cry 5 and Rise of the Tomb Raider.
When it comes to a showdown with a desktop RTX 3080 card, the XG Mobile has no chance. On the Far Cry 5 Ultra preset at 1080p, the desktop RTX 3080 Founders Edition can display an average of 165fps. That’s more than twice as good as the XG Mobile’s 78fps. The situation is similar with the demanding Metro: Exodus game, which takes full advantage of the RTX chips’ ray-tracing abilities. The XG Mobile achieved an average of 72ps on the in-game benchmark at 1080p and Extreme quality, compared with 101fps for the RTX 3080 Founders Edition.
You may be able to achieve better performance on some games by tweaking display-resolution settings if you have a 4K version of the Flow X13. When we test games on laptops, we set the game to output a full HD resolution, but we leave the screen resolution at its native setting. In most cases, gaming laptops have 1080p screens (and don’t have an eGPU attached!), so this shouldn’t affect results. But our Flow X13 review unit has a 4K (3,840 by 2,400) native resolution on the laptop panel. The test results above are at 1080p in the game settings, but with the panel left at default settings. When I dialed down the panel separately to full HD (1,920 by 1,200) in the Windows Settings app, I saw markedly improved results on Rise of the Tomb Raider: 118fps at the Very High preset and 131fps at the Medium preset, an improvement of more than 30% over the results in the chart above.
Other games also showed some improvement in this configuration, but the differences were far smaller. Metro Exodus and Far Cry 5 both saw improvements of less than 10% with the display resolution (in addition to the game resolution) set to full HD. It’s a good reminder that like many eGPUs, the XG Mobile requires a bit of trial and error to display games at peak performance.
Easy to Use, But Is It Worth the Money?
The XG Mobile is one of the easiest-to-use eGPUs we’ve tested, and certainly the most portable. It’s also quite versatile, with the ability to function as an I/O hub or dock, and stand in for your Flow X13’s AC adapter, in addition to its main function of boosting game performance. These qualities outweigh some of its more minor drawbacks, such as the fact that its proprietary connector is not compatible with any other laptop.
But the XG Mobile is costly and doesn’t perform as well as a laptop with a similar graphics processor built in. At $3,000 and up for the XG Mobile and the Flow X13, you’re spending at least $850 more than you would on an Alienware m15. In return for a lighter wallet, you get a far more portable laptop, but also one that performs worse even when the eGPU is connected.
Ultimately, the XG Mobile is the star of a shaky niche category of PC gaming hardware. Only a few shoppers can truly justify it. And there are even fewer now than there were last year, since many PC gamers are stuck at home in an era of social distancing, with no need to tote their gaming PCs around town. If you have a deep wallet, the XG Mobile is a cool toy, but we would rather save our money and accept the additional bulk and much greater capabilities of a laptop like the Alienware m15 R4.
[Editors’ Note: On Feb. 2, 2021, we added two paragraphs at the end of the performance discussion detailing additional game tests we did, at Asus’ recommendation, with the ROG Flow X13’s panel set to full HD (in addition to the game settings at 1080p). We did not change our final Editors’ Rating.]
