This article is about the Asus Zenbook S UX391 series, Asus’s new flagship clamshell thin-and-light ultraportable for 2018.
It’s meant to compete with the top contenders out there, like the
Dell XPS 13 9370 or the Huawei MateBook X Pro, with whom it shares a similar hardware platform, the compact and light build and the limited IO based entirely on USB-C ports.
We spent some time with an early sample of this laptop in the last few weeks and gathered all our impressions below, which are for the most part positive. Asus did a great job with the new design and addressed some of the issues encountered on their previous premium Zenbooks (
UX390, UX490), so as long as they don’t mess up with the quality control and availability, this Zenbook S UX391 will be one of the ultraportables to get in 2018.
Update: As for mid-2019, Asus offers the ZenBook UX392 in stores, a more refined follow-up of the device reviewed here, and
you can read all about it in our detailed analysis.
Read on for the whole story.
Specs as reviewed
Asus Zenbook S UX391 UA
Screen 13.3 inch, 1920 x 1080 px, IPS, non-touch, matte
Processor Intel KabyLake-R Core i5-8250U CPU
Video Intel UHD 620
Memory 8 GB LPDDR3 2133 MHz (soldered)
Storage 256 GB SSD (M.2 NVMe 80 mm)
Connectivity Wireless AC (Intel AC 8265), Bluetooth 4.1
Ports 1x USB 3.1 Type-C gen 1, 2x USB-C with Thunderbolt 3, mic/headphone
Baterry 50 Wh, 45 Wh
Operating system Windows 10
Size ~ 311 mm or 12.24” (w) x 213 mm or 8.38” (d) x 15 mm or 0.59” (h)
Weight 2.2 lbs (995 g) + 0.47 lbs (215 g) power brick, US model
Extras backlit keyboard, VGA webcam, available in Deep Dive Blue and Burgundy Red
As of the second half of the year, there’s also an updated Zenbook S UX391FA version in stores, similar to the one reviewed here in every aspect, but with the
more recent Intel Whiskey Lake hardware (Core i5-8265U and i7-8565U CPUs). As you might know by now, these are merely incremental updates of the previous KabyLake-R platforms, with merely slightly higher Turbo Boost speeds, so everything you’ll find in this article applies to the Whiskey Lake configurations as well.
Design and first look
The UX391 borrows design elements from the
Asus Zenbook 3s and the business B9440 models of last year, as the screen raises the main body in order to create a downward-inclined typing position and leave extra room for ventilation underneath.
The build and overall craftsmanship quality are top notches. Metal is used for the entire outer-case and the inner chassis, and there’s very little flex or give in either the lid-cover or the main deck.
The laptop is also subtle in design, with a dark-blue metallic color scheme, limited branding elements and only a hint of glam in the crude beveled edge around the hood. We’ve seen many beautiful Zenbooks in the past, but this one is one of my all time favorites.
As far as practicality goes, the Zenbook UX391 is thin and light, tipping the scales at under 1 kilo, but also compact, as you can tell from the small bezels around the screen. They’re not as narrow as on the
Dell XPS 13, but they’re close and at least allow room for the camera and microphones to be placed on top of the display.
With the laptop closed, you’ll notice there’s a crease on the front lip to grab and lift the screen from. That’s nearly possible with a single hand, but due to the design, you’ll probably find it easier to use both hands. As I mentioned earlier, the screen attaches to the laptop’s main body underneath, in a way that it lifts the main deck by about 2 cm, as you can see from the pictures included here. That creates an inclined ergonomic typing position on one hand, which corroborated with the blunt lips around the front and sides make for an excellent experience with everyday use, and also allows better airflow underneath, which has been one of my complaints with the existing Zenbook 3 lines.
A potential downside of this approach is that fact that all the hot air is pushed now towards the screen, but based on our tests that shouldn’t be an issue, as the bottom part of the display, around the Asus Zenbook logo, never gets past 45 degrees Celsius, not even with continuous demanding loads. On top of that, the exhaust grills are generous and there’s enough space between them and the screen to keep temperatures at bay.
Another aspect worth mentioning here is the rather precarious grip this computer has on a desk, since it sits on those tiny plastic feet at the bottom of the screen and not on all 4 rubber feet, like most other Zenbooks. That’s something to keep in mind. And then there’s also the fact that the screen only leans back to about 145 degrees, which suffices for desk work but can be a little limiting while lying in bed or on the sofa.
As far as the IO goes, the Zenbook UX391UA follows the current trend of minimizing ports to USB-C only, and as a result, you’ll only find 3 USB-C slots on this computer and a headphone jack. Asus will probably offer an adapter with USB-A and HDMI in the pack though (not included with this test unit), so at least you won’t have to buy one yourself like with most other options on the market.
All in all, the Zenbook UX391 is thin, light, well crafted, subtle and practically designed. As long as you can live with the USB-C only IO, there’s really very little not to like here.
Keyboard and trackpad
The keyboard on this Zenbook UX391 feels very similar to the one on the Zenbook UX490, with a slight layout twist, but otherwise similar feedback.
That layout twist is the fact that Asus inter-switched the Delete and Power keys, and thus the Power Button is no longer the top-right key that you’ll keep pressing my mistake when looking for Delete. The Power button is also a little harder to press than the keys around, so the chance of accidentally putting the computer to sleep (if you don’t disable this in the settings) is greatly reduced here.
The typing experience is right up my alley. The keys are a tad soft and mushy and only travel 1.2 mm into the frame, but I did enjoy the overall response, speed, and feedback. The keys are also backlit (in yellow) and you can choose between three different brightness levels.
On the other hand, I do have to mention that this keyboard is a little on the chatty side, so if you plan to use it in very quiet places at the library or school, you might catch some eyes.
For the clickpad Asus went with a Precision surface made out of the glass, which is both smooth to the touch and works great with everyday taps, swipes, and gestures. Asus had a lot of issues with glitchy trackpads in the past, but this one surprisingly worked flawlessly. Even the click buttons are nice, so perhaps if I were to nitpick, my only complaint would be the slightly smaller height of this clickpad, caused by the overall design that leads to a smaller palm-rest than on most other 13-inch ultraportables.
Asus also integrates an useful finger-sensor within the clickpad. It works well, yet some of you might not like this kind of implementation, as the cursor no longer tracks when your fingers get on top of the sensor. It didn’t bother me though and hasn’t bothered me on other laptops with a similar design in the past either.
This Zenbook gets a 13.3-inch display with fairly narrow bezels and matte finishing.
Asus went with a pretty good IPS panel, the same one they’re using on the Zenbook UX331, with above average brightness, contrast, and color reproduction, as you can see below:
Panel HardwareID: AU Optronics AUO492D (B133HAN04.9);
Coverage: 95% sRGB, 71% NTSC, 74% AdobeRGB;
Measured gamma: 2.3;
Max brightness in the middle of the screen: 285 cd/m2 on power;
Contrast at max brightness: 630:1;
White point: 7300 K;
Black on max brightness: 0.45 cd/m2;
Average DeltaE: 1.99 uncalibrated, 1.93 calibrated.
Keep in mind our Spyder4 sensor records lower brightness levels than other sensors, so in reality, this a 300+ nits panel, which corroborated with the non-glare coating will allow you to use the UX391 comfortably in bright places and even outdoors. On the other hand, if you truly need a bright screen, you’ll find better with the Dell XPS and a few other options on the market.
It’s also worth noting that the screen does not use PWM modulation with lower brightness levels.
Hardware, performance and upgrade options
The Asus Zenbook UX391UA is built on Intel’s latest hardware platform at the time of this article and we got to test the base-level configuration, and the one that will probably make the most sense for most potential buyers anyway. This one comes with the Intel Core i5-8250U processor, 8 GB of RAM and a 256 GB SSD.
If you open up the laptop you’ll notice that the RAM is soldered and non-upgradeable, but you can replace the included storage drive. Our test unit only gets a SATA M.2 drive, and if Asus decides to ship the final retail units with the same one, you’ll probably want to replace it with a faster NVMe drive yourself.
You’ll have to remove the entire back panel in order to get to the components, and for that, you’ll need to unscrew the Torx T5 screws visible around its sides and then just pop it out with a plastic card or prying tool.
Let’s get to how this laptop performs. I’d reckon most people will buy such a computer for everyday use, for browsing and multimedia content and music and so on. Well, the UX391 can handle such tasks easily, while running mostly cool and quiet. The pictures below show the HWInfo logs with speeds and temperatures while performing such daily chores.
Some of you might want to push it through more demanding loads (edit photos and videos, run programming software, perhaps run some games), and in order to do that, we ran our standard set of benchmarks and games on this sample. You’ll find the benchmark results below:
3DMark 11: P1957 (Graphics: 1758, Physics: 6669);
3DMark 13: Sky Driver – 4426, Fire Strike – 1117, TimeSpy – 389;
3DMark 13 Graphics: Sky Driver – 4135, Fire Strike – 1201, TimeSpy – 338;
PCMark 08: Home Conventional – 3401;
PCMark 10: 3594;
PassMark: Rating: 2959, CPU mark: 8031, 3D Graphics Mark: 738;
GeekBench 3 32-bit: Single-Core: 3517, Multi-core: 13695;
GeekBench 4 64-bit: Single-Core: 4182, Multi-core: 14280;
CineBench 11.5: OpenGL 45.93 fps, CPU 5.67 pts, CPU Single Core 1.62 pts;
CineBench R15: OpenGL 55.23 fps, CPU 525 cb, CPU Single Core 141 cb;
x264 HD Benchmark 4.0 32-bit: Pass 1 – 164.17 fps, Pass 2 – 33.98 fps.
I also added HWinfo logs from Cinebench and 3DMark and you’ll notice the CPU works just as expected while the laptop is plugged into the wall.
Running Cinebench in a loop causes the results to drop as the CPU heats up and has to clock down earlier, but as you’ll see in the logs it doesn’t go under 2.2 GHz, which is the standard Turbo Frequency for multi-core 100% loads.
With games, on the other hand, the CPU drops quickly to its stock speed of around 1.6 GHz, but with Intel UHD 620 graphics, this is not a gaming computer in the first place anyway. Still, it should handle older or simpler titles fine, within the platform’s limitations. As a side note, we didn’t spot any difference while gaming on battery or when plugged in, so you can actually play games on the go until you run out of juice (after about 2 hours). Cinebench and other high-CPU load performance, on the other hand, differ when the laptop runs on battery.
All in all, this Zenbook UX391 sample performed solidly in our tests and was able to squeeze as much as possible from the Intel KabyLake-R platform that it’s built on, which is surprising for such a thin-and-light computer, especially given last year’s Zenbooks struggled with throttling and performance drops.
Noise, Heat, Connectivity, speakers, and others
The cooling solution is simple, with a single fan and one narrow heatpipe.
The redesign of the UX391 allows for better airflow though, as there’s now an air intake grill on the laptop’s underbelly on top of the heatpipe and fan, and due to the fact that the main body raises on the screen there’s also more space between the desk and the components, plus the exhaust is more generous as well when compared to the UX390 and UX490 models.
Even so, this remains a thin laptop with a quad-core processor inside, so the fan is active all the time with daily use, however, it’s mostly quiet while watching movies. It ramps up with multitasking or when installing software, but even in this case it doesn’t jump above 38-40 dB at head level, but you will hear it in quiet rooms. I also noticed some slight electronic noise on our test unit, fairly audible in quiet environments from a normal working distance, but not in noisier places.
The fan remains quiet even with continuous loads. We measured noise volumes of up to 40-41 dB at head level with heavy multitasking and gaming, which is quieter than on most other laptops in this niche. On top of that, the fan quiets down quickly once ending the loads and gets back to the inaudible levels in a matter of 5-10 seconds.
As far as temperatures go, the Zenbook UX391 runs coolly with movies and everyday tasks but can get quite hot when stressed for a longer period of time. That’s perfectly normal on such a computer though and most of the areas that the users would come in contact with only get to low 40s.
*Daily Use – 1080p Youtube clip in EDGE for 30 minutes
*Load – playing NFS: Most Wanted for 30 minutes
For connectivity, Asus went with the Intel 8265 wireless module that provides Wireless AC and Bluetooth. This is a solid performer both near the router and at 30 feet with one wall in between, and I didn’t run into any disconnects or other sorts of issues during my time with this Zenbook. Wireless performance has been a sensitive topic on recent Zenbooks, but this UX391 sample performed flawlessly and hopefully, Asus won’t have QC issues with these new models anymore.
As far as the speakers go, they’re placed on the bottom and they’re similar to the ones on the Zenbook UX370 and UX331. The two speakers are punchy, at up to 85 dB at head level in our tests, but they distort a little at maximum volumes and you’ll probably want to use them below 80% to prevent those and the slight vibrations they push into the metallic palm-rest. All in all the Zenbook UX391 throws out some decent and punchy sound that should satisfy most of you.
The last thing on the list is the webcam, which unfortunately is the same crap VGA camera that we’ve seen on the UX390 and other premium Zenbooks in 2017. It’s placed on top of the screen, but the quality is poor.
There’s a 50 Wh battery inside the Zenbook UX391, just like on the UX331 series, which is averagely sized for this day and age.
Since the battery life does not disappoint and this laptop is a thin-and-light, I’d reckon most potential buyers won’t complain about it, but I would have liked a larger battery nonetheless. Here’s what to expect, with the screen’s brightness set at around 120 nits (~30 brightness).
6.9 W (~7 h 15 min of use) – very light browsing and text editing in Google Drive, Balanced Mode, screen at 30%, Wi-Fi ON;
6.8 W (~7 h 20 min of use) – 1080p fullscreen video on Youtube in Internet Explorer, Balanced Mode, screen at 30%, Wi-Fi ON;
4.5 W (~11 h of use) – 1080p fullscreen .mkv video in the Movie app, Balanced Mode, screen at 30%, Wi-Fi ON;
5.1 W (~10 h of use) – 4K fullscreen .mkv video in the Movie app, Balanced Mode, screen at 30%, Wi-Fi ON;
13.8 W (~3 h 30 min of use) – heavy browsing in Edge, Balanced Mode, screen at 30%, Wi-Fi ON;
27.5 W (~1 h 45 min of use) – gaming, Balanced Mode, screen at 30%, Wi-Fi ON.
Asus pairs this with a 45 Wh charger with quick-charging and a full-recharge takes around 1 hour and 30 minutes. The wall plug is integrated within the power brick, with non-retractable prongs, like on most other modern Zenbooks.
Price and availability
The Zenbook UX391 is available in stores, with prices starting from as low as $899 for a Core i5 configuration, while the higher-end options are also competitively priced in this niche.
Follow this link for updated configurations and prices at the time you’re reading the article.
There’s a lot to like about the Zenbook UX391 and I believe it’s a solid addition to the Zenbook family, next to the gaming-oriented UX331 series with dedicated Nvidia graphics.
When you draw the line, there’s very little wrong with this laptop. It’s thin and light, it’s fairly well built, it gets a good keyboard/trackpad, a pretty solid matte screen and performs surprisingly well given that the hardware is squeezed inside such an ultra-compact shell.
But while Asus has stepped up their game from the previous 13-inch Zenbooks and even last year’s Zenbook Primes, the competition in the segment is fiercer than ever. Laptops like the
Dell XPS 13, Huawei MateBook X Pro and especially the 2018 version of the LG Gram 13 are worthy alternatives that potential consumers should check out. The XPS gets Thunderbolt 3 connectivity, a brighter FHD screen and a 52 Wh battery, with a starting price of $1200 for a mid-range configuration. The MateBook starts at under $1000 and offers a 3:2 display, but also loses on battery life due to its 40 Wh battery. That new LG, on the other hand, is hard to beat, as it gets full-size IO and a 72 Wh battery for under $1200.
Knowing Asus, they’ll probably outmatch the competition price-wise, so those of you looking for a well-balanced ultraportable around the 1 kilo and $1200 mark should definitely have it on your list. I also expect this Zenbook to be competitive outside the US market, where those alternatives above are either not available or very expensive. Still, those of you interested in all day runtimes and features like an SD card-reader or fast PCIe storage out of the box might want to look elsewhere.
Update: As for mid-2019, Asus offers the ZenBook UX392 in stores, a more refined follow-up of the device reviewed here, and
you can read all about it in our detailed analysis.
Anyway, that’s about all I have to say about the Zenbook S UX391UA for now, but get in touch in the comments section if you have anything to add or any questions.
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Andrei Girbea Andrei Girbea, Editor-in-Chief
. I've a Bachelor's in Computer Engineering and I've been covering mobile technology since the 2000s. You'll mostly find reviews and thorough guides written by me here on the site, as well as some occasional first-impression articles.
June 7, 2018 at 3:41 pm
Notebookcheck preview shows huge throttling.
Can you investigate that a bit and see if undervolting helps?
June 7, 2018 at 3:42 pm
June 7, 2018 at 4:18 pm
Mine did not throttle badly, you can see the hwinfo logs in the article . I had the i5 though, the i7 might not do that well.
June 13, 2018 at 1:27 pm
My concern is the keyboard. I have the Zenbook 3 UX390 and I am disappointed with that keyboard. Is the keyboard of the Zenbook S UX391 much better or not? If not, what would you recommend? How is the keyboard of the Matebook XPro? I read the X1 Carbon has the best keyboard but it is very expensive. Thanks.
June 14, 2018 at 9:13 am
The keyboard on the UX391 is better imo, but I was also quite happy with the low travel keyboard on the UX390. Haven't got my hands on the Matebook yet, the Huawei laptops are not available over here.
June 13, 2018 at 5:25 pm
Thanks for the review. I was extremely happy Asus finally switched power/delete button. However, on all official images and various YT reports, power button is still the last one (like with all Asus models). Strange…
June 20, 2018 at 12:51 pm
Sorry to bother again. I am curious, why did Dell abandon the keyboard tilting design of the Adamo XPS? Is it because customers were not happy? Is it because with that design the laptop is not very stable? Because the tilting of the display has to go all the way back? Before buying, I am a little concern with that innovative design. Thanks.
June 20, 2018 at 3:40 pm
I found this kind of hinge pretty stable on both this Zenbook and the Vivobook that I tested earlier. My only concern would be that the small rubber feet that the screen rests on will wear off in time.
September 8, 2018 at 10:13 am
I bought the Zenbook S three or four weeks ago. Unfortunately, what I feared, has materialized. After tilting the monitor back, the right side corner of the laptop does not touch the desk, it remains a little higher, and it is worsening with use. There must be a hinge problem. Very disappointed. Can it be fixed?
September 10, 2018 at 1:03 pm
I don't think so. Poor quality control on your unit. My test unit sit stable on all its legs. I'd ask for an exchange.
July 15, 2018 at 4:53 pm
I just noticed something very strange. Your model has an air intake vent on the bottom, while notebookchecks does not, why is this?
And could you check if the thunderbolt is 4x with full bandwidth?
July 17, 2018 at 11:26 am
Good questions. Mine was preproduction, perhaps they decided to opt for taking it out on the final units, which could explain he throttling issues. Should further look into it.
July 17, 2018 at 1:37 am
Is this laptop good enough for photo editing? I'm using Lightroom for photo edit.
But I don't know if the i7-8550U can handle the job or not? Or should look for a notebook with normal voltage cpu?
July 17, 2018 at 11:27 am
I'd look at a standard-voltage CPU laptop if possible.
August 31, 2018 at 12:20 pm
One thing I would like to know is compatibility with egpu. Helped my friend with his prev zenbook pro ux501 which was frustratingly difficult. Was able to plug akitio node and asus xg station to a xps 9560, but zenbook simply refused (at the same time we were not that techie ourselves 😬). I thought xg being an asus should have worked but nope
August 31, 2018 at 1:05 pm
I don't have an eGPU, so never tested that out. Doug has one and he might have tested it on the Zenbook UX550. Not the same laptop, but still an Asus, so I'll ask him about it.
August 31, 2018 at 1:06 pm
Thank You VM. Not much articles about asus laptops with egpu variants
August 31, 2018 at 1:29 pm
Doug says his Mantiz Venus worked fine with the Zenbook UX550VE. Of course, that's no guarantee this Zenbook S will work as smoothly, especially since it's a different hardware platform, but I'd reckon it might… Sry I can't be of more assistance. You could also drop a question in this article and perhaps some of the people still following the comments could help more: https://www.ultrabookreview.com/10761-razer-core-review/
December 5, 2018 at 3:10 am
So, just to update if someone is thinking about the Asus UX391UA to pair with an eGPU.
This laptop just do not work with many eGPUs. This laptop do not work the Mantiz Venus and also does not work with Asus own Rog XG Station 2.
I RMA this laptop to Asus so that they try to fix an on and off problem (connecting and disconnecting). They couldn't, and told me that this laptop is not compatible with the Mantiz Venus and also with the Rog XG Station 2 they tested with. They say that the laptop is only guarantee compatible with the XG Station Pro.
So, if someone reading this is thinking about the Asus UX391UA to pair with an eGPU, don't do it, it just won't work.
September 16, 2018 at 6:23 pm
Hi, does UX491 UA/FA support 4x PCIe lanes for Thunderbolt 3 port? And does it support OPI 4GT/s Mode?
September 17, 2018 at 12:27 pm
Unfortunately I forgot to check at the time of the article. I'd expect they're 2x PCIe each, so OPI 2GT/s, but I could be wrong. Perhaps you can contact Asus support and ask them about it, hopefully they'll have a proper answer
September 18, 2018 at 10:25 am
Thanks for your reply, Andrei.
September 21, 2018 at 9:19 am
No one seems to have addressed this but I am concerned about how the ergolift will work if there isn't enough desk space for all the feet. What happens if three quarters of the laptop is on a desk and the other quarter is jutting off the edge? What about half on half off? Does the whole laptop slide down and go crashing to the floor? What about if the back is hanging off an edge? Will it flip backwards and go crashing as well? Also am not sure how to hold the laptop in one hand. Usually you can just wrap your fingers around the back on a normal laptop and support it fully. If you do that with this laptop there will be a large gap and any hand movements will move the screen on its hinge. I am also concerned about the typing angle. The recently announced ux333/ux433/ux533 look to have a reasonable typing angle increase, but the ux391 typing angle seems awkwardly huge?
September 21, 2018 at 2:54 pm
Most laptops are unstable if they don't sit on all their feet, although designs with long feet like the XPS 13 are the exception.
Now, this design is probably not for everyone and not necessarily the best either. Should work for most people who just keep their laptop on a desk or on the lap/legs, I think it's going to work just fine. And the angle is actually fine, this laptop is small and I'd reckon that makes it look bigger than it actually is. I worry about QC control though, which could cause the front feet and the back hinge to be misaligned, as someone else already mentioned in the comments.
October 12, 2018 at 9:44 pm
"with good brightness" – Max brightness in the middle of the screen: 285 cd/m2 on power;
You think that brightness is good ?
I will remind you
Brightness Dell XPS 13 9370 => 399
Huawei MateBook X Pro 495 cd/m²
Macbook pro 13 2018 495 cd/m2
October 13, 2018 at 11:00 am
Perhaps "good" is a bit of an overstatement, but it's above average, and if you kept reading, I mentioned our sensor detects lower levels, so in reality it's at about 300 nits. Yes, there are brighter options out there, but the XPS 13 is the only real alternative, as the others you mentioned have a glass layer and/or are more expensive.
October 14, 2018 at 2:20 am
OK . All the same, compared the older generation it's not good . For example Zenbook UX303LN has been 344 cd/m². Unfortunately asus regressed
October 15, 2018 at 11:51 am
You're right, but personally I find a 300-nits matte panel good enough for everyday use, even in brighter light. I'd guess it's up to each of us to decide on their threshold.
Shaw X. Tan
December 31, 2018 at 7:33 pm
"USB-C only" is a Pro to me. I completely moved away from other variants of USB a few years ago – yes it's possible without dongles, just invest in some new cables and accessories! I sold my Kindle Paperwhite because it doesn't have a USB-C, and I won't buy a new one until it does.
My Sonic toothbrush charges with a Qi wireless charging pad which has a USB-C connector. I did a few mods to gadgets too, including an alarm clock is now using standard USB-C PD charger happily. I'm considering a beautiful coffee scale (https://www.espressogear.com/index.php?route=product/product&product_id=9092), because it has a USB-C for charging and temperature readings.
I wouldn't buy the new laptops ASUS announced this year, because they put the ugly USB-A back.
September 7, 2019 at 6:23 am
Link to the calibrated display profile is not working – can you fix it?
Thanks a lot!
September 9, 2019 at 9:45 am
Looks like I didn't save the profile for the laptop, sry for the inconvenience.
November 16, 2019 at 5:33 pm
The UX391FA with the 8565U is a big improvement over the UX391UA you reviewed, I've tested both. The UX391FA has a semi-passive fan that is turned off most of the time and only turns on under high heat, and turns back off again very quickly. You can also set a silent fan profile in the MyASUS app that limits the max RPM to extremely quiet levels without lowering boost TDP. It also boosts to a much higher TDP and the screen is excellent in the 4K touch version. My 4K screen has a JDI (Japan Display) IPS panel (model JDI LPM133M385A) with an incredible 1600:1 contrast ratio measured with my Spyder5. Also 100% sRGB but Adobe RGB is just average so it's not wide gamut. However, it has the best black level of any IPS I have ever seen and peak brightness is high too. I was extremely surprised at the JDI panel since they usually make high end IPS displays for Apple and Zenbooks are very hit and miss when it comes to panel quality. Maybe I got lucky, though the ZenBook S 4K version is considered a flagship ultrabook product too…
I also compared to the UX392 and found the UX391FA to be much better despite that the UX392 has two fans. The UX392 has loud fans that are always active, yet the UX391 performed better with it's one semi-passive fan. It boosted to a higher TDP and also kept a high TDP in silent fan profile, while the UX392 cripped performance with a 5W CPU TDP in silent fan profile.