Original Link: http://www.anandtech.com/show/7838/dell-xps-15-haswell-edition-qhd-with-a-refined-design

Last year one of the better Windows laptops I encountered, at least based on the core appearance and design, was the Dell XPS 15 (Ivy Bridge Edition). It was basically Dell's third attempt at making a MacBook Pro (more or less) – the first two attempts being the Arrandale XPS 15 (with the Sandy Bridge model using the same design), then there was the XPS 15z that used dual-core Sandy Bridge in a slimmer form factor, and then the retooled XPS 15. Today we have the fourth generation XPS 15, which has taken many of the design elements of the IVB XPS 15 but hopefully fixes the cooling/throttling, adds a Haswell CPU and an updated 700M NVIDIA GPU, ditches the optical drive, and on the higher-end SKUs you get an ultra-high resolution 3200x1800 display. The display is actually both good and bad, but I'll get to that later. Let's start with the core specifications for the high-end model, which is what I received for review.

Dell XPS 15 (9530) Specifications
Processor Intel Core i7-4702MQ
(Quad-core 2.2-3.2GHz, 6MB L3, 22nm, 37W)
Chipset HM87
Memory 2x8GB DDR3-1600
Graphics GeForce GT 750M 2GB GDDR5
(384 cores, 967MHz + Boost 2.0, 5GHz GDDR5)

Intel HD Graphics 4600
(20 EUs at 400-1150MHz)
Display 15.6" Glossy PPS 16:9 QHD+ (3200x1800)
(Sharp LQ156Z1 Touchscreen)
Storage 512GB mSATA SSD (Samsung SM841)
Optical Drive N/A
Networking 802.11ac WiFi (Intel Dual-Band AC-7260)
(2x2:2 867Mbps capable)
Bluetooth 4.0 (Intel)
Audio Realtek HD
Stereo Speakers
Headset jack
Battery/Power 9-cell, 11.1V, 8000mAh, 91Wh
130W Max AC Adapter
Front Side N/A
Left Side Battery Charge Indicator LEDs
Headset jack
2 x USB 3.0
1 x Mini-DisplayPort
1 x HDMI
AC Power Connection
Right Side Flash Reader (MMC/SD)
1 x USB 3.0
1 x USB 3.0 (Sleep Charging)
Kensington Lock
Back Side Exhaust vent (inside LCD hinge)
Operating System Windows 8.1 64-bit
Dimensions 14.6" x 10.0" x 0.3-0.7" (WxDxH)
(372mm x 254mm x 8-18mm)
Weight 4.44 lbs (2.01kg)
Extras 720p HD Webcam
87-Key Backlit Keyboard
Pricing $2300 as configured
$1500, $1750, and $1950 alternatives

As is often the case, the new XPS 15 with Haswell is both better and worse than Apple's latest MacBook Pro Retina – and that's just looking at the paper specifications. The display is higher resolution than the Retina, with a 3200x1800 panel compared to Apple's 2880x1800 resolution display. Apple has been one of the few companies to continue to buck the trend towards 16:9 aspect ratio displays, sticking with a 16:10 AR – a choice I wholeheartedly approve of. The 3200x1800 panel is the 16:9 alternative to the rMBP 15's panel, and while Dell technically has more pixels, I still would prefer the “taller” screen that Apple uses. (We'll also need to look at color accuracy, but that we’ll get to that later in the review.)

The display is actually one of the few areas where Dell comes out ahead, however. In most other areas, the laptops are either equal or Apple maintains their lead. For example, Apple is now using PCIe based SSDs while Dell is using a Samsung SM841 SSD mSATA drive – it’s not that the SM841 is slow, but the PCIe SSDs are certainly faster. For the CPU, Apple has elected to use Intel's latest Crystalwell chips with Iris Pro Graphics (i7-4750HQ and i7-4850HQ) while Dell is opting for the 37W quad-core i7-4702HQ. It's not a huge difference in performance – the maximum CPU clock is 3.5GHz on the 4850HQ compared to 3.2GHz on the 4702HQ and 4750HQ – but Apple still comes out ahead thanks to the “L4 cache” (eDRAM). On the GPU front, both systems use NVIDIA's GT 750M GDDR5 chip, so the difference in iGPU performance is largely superfluous. Interestingly, it appears the main reason for the difference in CPUs (other than Dell not being interested in Crystalwell) is TDP, and in fact the base clock of the 4702HQ is actually slightly higher than the base clock of the 4750HQ.

Worth mention is that there are three different models of the new XPS 15 available right now. The base model XPS 15 comes with a 1920x1080 touchscreen display (it’s not clear if this is a TN panel or not), 500GB HDD with 32GB SSD cache, dual-core i5-4200H CPU, 8GB RAM, integrated HD 4400 Graphics, and a 61Wh battery for $1500 (or a 3-year warranty for $1750). Stepping up to the $1950 XPS 15 will get you the quad-core i7-4702HQ CPU, 3200x1800 PPS (similar to IPS) touchscreen, 16GB RAM, GT 750M GDDR5 GPU, a 1TB HDD with 32GB SSD cache, and a 61Wh battery. And then there's the big kahuna that we're reviewing, which is mostly the same as the $1950 model but it dumps HDD storage completely in favor of a 512GB mSATA SSD and adds a larger 91Wh battery in place of the 2.5” drive. $400 extra for a 512GB Samsung SM841 is actually a pretty reasonable expense, considering retail pricing on that SSD is typically well over $500, making the added battery capacity a bonus. Of course Dell isn’t paying retail prices, and drives like the Crucial M500 480GB mSATA can be had for $320 online, but even then the $400 upgrade price is still reasonable.

The components aren't the only change with this model. The design language of the latest XPS 12 and XPS 13 carries over now as well, with carbon fiber being used on the bottom casing of the chassis. Perhaps more noteworthy is that Dell has ditched the optical drive this time around, and on the highest end model they also skip out on conventional storage. Both changes make room for additional battery capacity, where the model we're reviewing comes with a 91Wh battery. Dell also manages to stuff all of these updates into a thinner and lighter chassis – the new model we have weighs 4.44 lbs. (2.01kg) while the previous generation weighed 5.79 lbs. (2.6kg), and this generation is 0.7” (18mm) thick compared to 0.91” (23.2mm) previously.

Of course, besides the core hardware and other design elements, the big question people undoubtedly have is going to be thermals. Dell let me know that thanks to our investigation of the thermal throttling on the earlier IVB XPS 15, they went back and redesigned the cooling. Like the rMBP 15 and a few other laptops, Dell is now using a dual cooling solution for the CPU and GPU with two fans (the removal of the optical drive makes way for the second fan). I've run through our benchmark suite, and I’ll discuss later the question of throttling and whether or not that’s a concern. Using some pathological workloads and stressing both the CPU and GPU (e.g. Cinebench on seven of the eight CPU cores and a GPU load like 3DMark), it’s definitely possible to exceed the thermal design of the XPS 15 and end up with lower clocks, but there’s more to it than that. How much of a concern this is can largely be answered by the question, “Do you play modern PC games?”

Not surprisingly, the host of changes listed above makes for a much more interesting laptop, but one that can end up costing a fair amount of money. Given that only the top model sports pure SSD storage, that's the one we need to compare with Apple's rMBP 15, and it mostly ends up a wash. You can get the Dell for $2300, as mentioned already. The rMBP 15 with 512GB SSD on the other hand will set you back $2600. Apple gives you a faster SSD (PCIe based), a faster CPU (i7-4850HQ), and Thunderbolt 2, which makes the extra $300 acceptable. (Other options for right around the same price are available, for example this one gets the i7-4950HQ CPU but uses Iris Pro Graphics and only comes with 8GB RAM.) Dell's model has a larger battery (but likely less battery life if we compare Windows 8.1 with OS X Mavericks), a touchscreen, and a higher resolution display. Ultimately, it's likely going to be more a question of whether you're interested in running OS X or Windows 8.1.

I do have to say that I also miss the ability to custom configure Dell’s laptops, and perhaps that’s just the way things will be with systems like this that target style more than pure performance. I’d love to have the option to configure the storage, display, CPU, RAM, battery, and GPU options rather than choosing between one of three pre-configured models but that’s just not in the cards right now. Anyway, with the overview of the core components out of the way, let’s find out how the XPS 15 performs, what's it like using a high-DPI display in Windows 8.1, and how the laptop fares in everyday use.

Dell XPS 15 Subjective Thoughts: Life on the High-DPI Edge

We like to start every laptop review with our subjective impressions of the system in day-to-day use. Here, the XPS 15 really does well, as the design looks great and at least in my experience feels great as well. The build quality is solid and I would say this may be the best Dell laptop I’ve ever encountered in terms of the look and feel. The touchpad and keyboard work just as they should, with a good feel and responsiveness. This is such a rarity that it still boggles my mind – getting the basic input devices more or less right should be something from Laptops 101, but somehow there are a lot of laptops with terrible touchpads and/or funky keyboard layouts. I still miss having dedicated document navigation keys and a “Context Key” (Shift+F10 equivalent), but I’ve adapted to the XPS 15 layout with no substantive issues.

There were a few oddities that did come up in testing – the big one being that at times, the touchpad and touchscreen basically stopped working properly for “clicks”. I could move the mouse cursor around, but as soon as I tried to click it appeared that the OS was sending that click to the far reaches of space. The active application would lose focus, and pretty much nothing would happen. The solution was to reboot, which seems pretty crazy as a “solution”, but I think I tracked down the issue to updating video drivers. Normally, that’s a simple process, and in some cases NVIDIA and AMD are able to update the drivers without a reboot. Well, perhaps thanks to the high-DPI display or some other factor, every time I’ve updated the NVIDIA drivers I’ve ended up needing to reboot (via keyboard shortcuts no less) in order to get proper mouse functions back. This is a rare enough occurrence that the only reason I mention it is that it may help others, and perhaps the driver teams at Dell/Intel/NVIDIA may be able to fix the root cause.

Sound quality on the XPS 15 continues to be decent, particularly for this size/thickness. Bass response isn’t really there and the earliest XPS 15 models sounded better, but that’s partly because they were a lot thicker and so there was more opportunity for putting in a subwoofer and perhaps getting better reverb/acoustics/whatever. Sorry if that’s not particularly technical – I’m not an audiophile by any stretch of the imagination; basically, I just go with what my ears tell me sounds good. Earphones of course will sound better than any laptop if you’re after true quality, but even without the XPS 15 sounds quite good. Perhaps more importantly, when listening to audio through the headset jack, I didn’t notice any static or other interference, which is definitely something that has come up with other laptops I’ve used.

Moving on to perhaps the most important aspects for many of you, let’s talk about the display and storage. I received the QHD+ panel for this review, and that tacks on quite a bit to the final price. The base model comes with a 1080p display, but there’s no way to get pure SSD storage unless you spring for the top-end model. That’s a bit of a misfire I’d say, as we’re fast approaching the point (or perhaps even past it) where including mechanical storage in a laptop is a serious faux pas – and for a high-end laptop like the XPS 15 that’s designed to compete with the likes of the Apple MacBook Pro line, there’s simply no reason for it. I also think Dell is being too conservative with the use of an mSATA SSD; I’m not sure how much of a difference it would make to go with an M.2 SSD (particularly a PCIe-based solution), but there are occasions where the SSD feels just a bit less responsive than some of the 2.5” SSDs I’m used to running. It’s still far better than any of the HDD + caching SSD laptops I’ve used, however, so unless you absolutely need maximum storage throughput, I wouldn’t worry too much about the use of Samsung’s SM841.

Subjectively, the 3200x1800 display on the Dell XPS 15 looks impressive out of the box – the pixels are fine enough that it's very difficult (perhaps impossible in my case, as my eyes aren’t what they used to be) to see them with the naked eye, and with my basic lenses on my Nikon D3100 I likewise am unable to capture an image of the pixels. Within the Modern UI, everything works as expected as well – everything scales nicely and you simply use the applications as you would on any other tablet or laptop. Where things get messy is when you switch to a desktop application. People often argue about whether or not Windows handles DPI scaling well; my personal opinion is that it remains a mixed bag. Some things scale nicely and look as you would expect; others don't scale at all, and still others scale the size of text but not other elements. Some of this you can blame on the programmers behind the various applications, but particularly on programs that are several years old (but remain useful) we can't really expect new versions (for free) simply because Microsoft has a new way of doing scaling. There's also the question of how many applications really work well within the Modern UI, and again personally there are many times that I simply like the desktop view and don't want to lose that.

But what's a 3200x1800 display really like in Windows 8.1? There are a few options for how you want to run things. You can run at native resolution and use DPI scaling (100%, 125%, 150%, 200%, or some other custom number), or you can run at a lower resolution (like 1600x900 or 1920x1080) and just let the display scaling do the work. As you might suspect, neither option is perfect. 200% scaling in theory is pretty easy – you just double everything – but doubling images doesn't always look great and so apparently that doesn't happen, even with Windows 8.1. The result is that most apps look fine, but there are exceptions. And needless to say, anything running at an unscaled DPI looksreally tiny, for example the StarCraft II launcher looks is unscaled whereas Steam’s UI scales.

Here's a gallery showing just two instances of the scaling not doing what most people would expect. Look at the browser tabs in Chrome, where in one screen it's running at 1080p 100% and in the other it's at 3200x1800 200%. The second shows Steam and the StarCraft II launcher, with 125% and 200% DPI settings I believe; you can see SC2 is the same size in both images while everything else changes.

So those are a couple instances of DPI scaling not working, and it’s basically the fault of the developers, but if Microsoft wants this high-DPI stuff to really work then they need to find solutions to dealing with…let’s just call them “obstinate programmers”. Windows has been around for a long time and creating a new way of doing things (i.e. Modern) doesn’t help at all with existing programs. It’s one of the reasons I think a lot of people are sticking with Windows 7 for the time being. A proper solution needs to work for any reasonable application that someone might run, and perhaps give the user the option to enable/disable the scaling if it causes problems. For now, unless you’re ready to live mostly in the Modern UI (or have exceptional vision and can run at 100% scaling and 3200x1800), just know that there are going to be quirks to deal with.

Dell XPS 15: QHD+ LCD Testing

Considering that this is the first QHD+ display that I’ve tested in a laptop, I’m going to start our performance metrics there. We’re changing quite a few things with our laptop reviews for 2014 and moving forward, and one of the most important changes will be in the area of testing the displays. We’ll be using the same software and hardware that we use for testing desktop displays, and hopefully the results of our new testing will shake things up a bit in the laptop LCD world. Basically, we’re using CalMAN 5 to perform testing, and that now allows us to report uncalibrated as well as calibrated color results.

Update: After learning of the "Splendid mode" and "Generic color" options in the Windows Mobility Center settings on the XPS 15, I went back and revisited the subject of display accuracy/quality. You can read more in the full XPS 15 LCD update article. Note that most of the results below (other than the comparison charts) are from the initial testing.

The charts and images tell the story quite well, but the short summary is this: out of the box, most Windows laptops – including the new XPS 15 with a QHD+ display – deliver colors that seem to have more in common with fantasy land than they do with accuracy. Post-calibration the display does exceptionally well, but if you lack the proper hardware and software to calibrate your display (or if you’re running an application that bypasses the LCD LUTs), you’ll be stuck with less than ideal color reproduction. How important this is will depend on the individual, but for a top quality display we really want to see manufacturers take the time to do the display justice. $5 extra per system to properly factory calibrate the display would do wonders here – we don’t need perfection out of the box, but average DeltaE of less than 2 would certainly be desirable. And with that said, let’s start with the uncalibrated results.

The RGB values are very clearly nowhere near what they should be, with most blues being 10% too high and the reds being 15% too low. Likewise, the gamma – which should ideally be a flat line – looks more like a mountain and a valley. Grayscale DeltaE is only at acceptable levels for the darkest of shades – where it matters less – while everything above the 15% level ends up with a visible error of 5.5 to nearly 8.0. Colors are a bit better in most respects, with the blues generally being the farthest off of the target, but quite a few colors actually come in below a 3.0 DeltaE.

The one bright spot (literally) is that the display can get quite bright, which is good for outdoor use or when traveling. The display can reach a 450 nits (cd/m2), and the “auto-brightness” function tends to be a bit on the brighter side, which is the opposite of what I usually experience – I took the XPS 15 to CES and at one point in a presentation Anand was sitting next to me and complained the laptop was “too bright!” I had to disable the auto-brightness setting and manually drop the LCD down to 10% or so before it was acceptable. (Does anyone actually like auto-brightness adjustments on laptops? I’d personally just as soon manually tune the backlight to an acceptable level.) The contrast ratio is also very good, measuring around 1350:1. Part of that comes from the inaccurate colors, but it certainly gives the display some “pop”. Regardless, if you want accurate colors, you absolutely have to plan on calibrating the XPS 15 display. But when you do, things turn out very nice….

Post-calibration, color balance is close to perfect, the gamma is at least approaching a flat line (though still with bumps and valleys at the 5% and 95% marks), and DeltaE is well below 2.0 and often below 1.0, on both the grayscale and the color charts. There are still some errors in shades of blue, but those tend to be less visible to the human eye so it’s not a huge concern. Contrast ratio and maximum brightness take a hit from calibration, as the white levels are now where they should be, but the XPS 15 is still able to reach nearly 1150:1 contrast with a white level of 385 nits.

As far as viewing angles go, Dell is using something they call a PPS panel, which has a wide viewing angle…except it’s not quite the same as IPS. One of the big problems with TN panels is that the colors get all messed up with off-axis viewing, and in particular the vertical viewing angles can be problematic. Let me make it clear that the PPS display is not like TN, but the colors do seem to shift a bit from extreme angles. It’s not something I’d ever experience in normal use, but if I look from an oblique angle it doesn’t quite look like an IPS or VA panel. Or perhaps it’s just that I’ve never used a 15.6” QHD+ IPS panel before? Anyway, the panel is really a great display, but I do wish Dell had factory calibrated to really set it apart.

LCD Analysis - Contrast

LCD Analysis - White

LCD Analysis - Black

LCD Analysis - Delta E

LCD Analysis - Color Gamut

About that High-DPI Display….

Then there’s the whole DPI scaling aspect as it applies to Windows. Depending on whom you talk to, it’s either not a problem at all (which is true if you stay within the Modern UI), or it can be a huge mess. I tend to fall more into the latter camp, as there are a lot of applications I run that apparently have not been designed with DPI scaling in mind. A big one of these, amazingly, is Chrome – how arguably one of the best browsers still utterly fails to work right with DPI scaling is a mystery to me. But there are many others – FRAPS, older applications, CalMAN 5, and the launch screens for quite a few games all came up during the time I’ve used the XPS 15.

I don’t use a Mac, so I don’t know exactly how the day-to-day experience of a MacBook Pro Retina differs, but from what I’ve gathered Apple was able to jumpstart the support for high-DPI with their first party apps and likely just giving more attention to finer details of the implementation. There are apps that play fine with high-DPI on Windows, and basically all of the Modern apps work well, but I’m having a really difficult time letting go of my actual windows to run things in full screen/split screen modes. I do it all the time on a tablet, and it feels more or less natural, but I regularly have dozens of browser tabs open (in Chrome) and 10-15 other applications running, and switching between them using the existing taskbar just works better for me. Take that as you will, but basically there are still lots of applications out there where the developers haven’t addressed the question of high-DPI support – and for applications that were released more than a couple years ago that haven’t been updated, you can guess that they may never receive such support.

The great thing is that the DPI is so high that there’s a simple workaround if you are having issues with DPI scaling: run at a lower resolution and set the scaling to 100%. It’s actually what I ended up doing after a while, as 1080p 100% on a 15.6” display still feels much more useful to me than 3200x1800 with 200% (or even 150%) scaling. It’s a bit odd for me to finally have a high-DPI laptop and find that, no, I personally don’t really benefit from the higher resolutions. Then again, my eyesight at 40 years old is perhaps not the best starting point for this sort of thing, as even 15.6” 1080p can feel a bit small on text at times. Considering how much I’ve run this display at 1080p, though, I have to say that I’ve never really noticed that I wasn’t running at native resolution.

Dell XPS 15: Throttling or Not?

Before we get into the performance results, I want to veer off on a tangent for a bit. One of my biggest concerns with the new XPS 15 was whether there would be throttling – and if so, how it would take place. The previous XPS had a lot going for it, but the throttling was so bad that the discrete GPU was all but useless in practice. Here's a quick look at the internals of the new XPS 15, along with my attempts to improve cooling by replacing the thermal interface material.

So after unpacking the new XPS 15, the first thing I did was to start running some gaming benchmarks to see if any throttling was taking place. Everything looked good, with consistent performance in my first gaming benchmarks and GPU temperatures typically in the upper 70C range or lower. I continued on with running tests, found a few glitches that I brought up with Dell, and at one point a driver update from NVIDIA came out.

The initial drivers (Intel and NVIDIA) had an issue where playing games at non-native resulted in severe letterboxing (basically everything ran at 1:1 pixels on the display), so that was a problem that needed to be fixed. The updated drivers worked properly in this area, but as I commenced testing something became immediately apparent: GPU throttling was back, and it was quite severe. It’s at this point that I basically got lost in a web of troubleshooting, trying to figure out what was going on. Generally speaking, when the GPU hits 80C or more, the clocks start to drop, and in some cases things are apparently bad enough that the GPU simply gives up and runs at 135MHz core/405MHz GDDR5. As you can imagine, this makes running any game a very poor experience – running on just the iGPU would in most cases result in better performance.

So I rolled back the drivers, returned to the A00 BIOS, and tried many other things, all to no avail – I simply couldn’t reproduce my original gaming benchmark results. Then I opened the bottom of the laptop and tried running with the cover off, and things were a bit better, but there was still throttling and I couldn’t match the original scores. Much time and troubleshooting passed, and then I stumbled on a partial fix: running with the Balanced or Dell profiles appeared to produce better performance (and less throttling) than running on the High Performance profile…but some throttling still seemed to be going on.

By this time, I had two more or less identical XPS 15 laptops in house for testing and troubleshooting, both were behaving in a less than ideal manner as far as GPU clocks are concerned, and I decided I would make a video of the systems running the same tests side-by-side with one using the Dell power profile and the other using the Balanced power profile. In theory, these should be the same, other than the name, but I wasn’t quite sure. Before doing this, I also decided to make sure all the drivers, firmware, etc. were the same on both systems, so I grabbed the latest Dell and NVIDIA drivers, updated the BIOS to A02 on the original laptop, and got ready to shoot my video…and suddenly the throttling was gone…mostly. Ugh.

My best guess at this point was that an updated firmware that I applied for the touchscreen played a role, but I wasn’t certain of that. Running a pathological workload (e.g. Cinebench on seven CPU cores with Furmark on the GPU), it’s possible to get the GPU to throttle, but even there it’s not always as severe as what I experienced for a few weeks. As it stands, I have now tested the XPS 15 (many, many times!) in both 67F ambient and 80F ambient environments, and at least if it’s not too hot performance is basically where it should be for gaming. I haven’t found other talks of throttling either, so perhaps others were testing in cooler rooms or just not hitting the GPU as hard – or maybe it’s just a few specific games or other software where the issue crops up. To be clear, throttling of the GPU does still occur to some extent, but gaming really isn’t a top priority for this system and I think I’ve finally found the workaround.

To first illustrate what’s happening, here are the gaming performance results from my original testing (at our “Mainstream” settings), as well as testing with the latest drivers and firmware at ~67F and ~80F. I’ve normalized the performance to the 67F testing, and I don’t know what the ambient temperature was with my initial testing (probably around 70-75F).

Dell XPS Performance
  Initial Testing 67F Updated Testing 85F Updated Testing
Bioshock Infinite 112.1% 100.0% 100.0%
Elder Scrolls: Skyrim 102.5% 100.0% 99.9%
GRID 2 89.0% 100.0% 100.5%
Metro: Last Light 98.7% 100.0% 99.6%
Sleeping Dogs 100.7% 100.0% 99.6%
StarCraft II: HotS 98.6% 100.0% 99.8%
Tomb Raider 2013 106.7% 100.0% 99.8%

In nearly all cases, the performance is basically equal between the hot and cold testing with the latest drivers, meaning any throttling is mild to non-existent. But there’s still more to discuss. Specifically, I was having problems with GRID 2 being a bit sporadic; the first benchmark run was usually fine, but subsequent runs sometimes ended up with worst-case throttling. In fact just before wrapping up this review, GRID 2 was consistently getting stuck at minimum GPU clocks. In a final effort to figure out what was going on, I logged clocks and temperatures, then rebooted and tested some more. Bingo. For more than five benchmark runs in a row everything is running fine. Yeah, it’s that sort of problem. Here are two charts of GRID 2, with the same settings in both cases, taken within the past 30 minutes – one before rebooting, and one after rebooting:

As you can see, prior to the reboot I was seeing high temperatures and severe throttling. It’s not a gradual throttling before the cutoff either – one second the GPU clocks are at 940/2500MHz and the next they drop to 135/405MHz. The GPU core reaches 88-89C and the CPU hits a maximum of 96C in my first set of benchmarks. In contrast, after a reboot I’m seeing more gradual (sensible) GPU clocks, with a maximum GPU temperature of 81C and a maximum CPU temperature of 87C, with no serious issues.

My conclusion at this point is that there’s some service, driver, or firmware that has some issues, and over time – running without a reboot – this builds up until the above throttling takes place. What specific workload causes this isn’t quite clear; normally when I’m using a laptop I don’t tend to reboot it on a regular basis, and in some cases that can mean days of use running many applications – in fact most of my computers only get rebooted when I apply a new driver or a Windows Update requires it. Anyway, there’s an old joke of sorts with tech support where the solution to many computer problems is to reboot the system. While that may help in many cases – and it certainly does here – this isn’t really a true solution; it’s a workaround. If all the drivers and software are running properly, OS reboots are not required to “fix” anything. As I haven’t been able to determine what exactly causes the system to get backed into these higher temperatures/throttling, all I can say for now is that if you do happen to encounter this glitch, try rebooting.

To summarize then, I don’t really have any remaining serious concerns with the GPU throttling, given the above workaround. If it starts to happen, you’ll know, and while a reboot is inconvenient in my experience it’s not usually required. I do feel Dell was perhaps overly conservative with the fan speeds and target GPU temperatures – and the inherent fan noise – but after being burned by RMA issues with NVIDIA’s G84/G86 back in 2007, I don’t really blame them. I’ve used other laptops that get a lot louder than the XPS 15, but while that might be annoying, to their credit I didn’t see any weird throttling issues. But then, I’ve also never tested a laptop with a QHD+ display before, so that’s a potential root cause (i.e. Intel and/or NVIDIA graphics drivers, and possibly firmware as well). There are 14” laptops with faster GTX 765M GPUs that are basically as thin as the XPS 15 (MSI GE40 and the Razer Blade 14 for example), so it’s not just a matter of size – something else is at play here. If you’re mostly looking for a multimedia or business type laptop, the discrete GPU isn’t really even needed these days – it might have been nice to see a version of the XPS 15 that kept all the other high end features (QHD+ display, pure SSD storage, larger battery) but dropped the GT 750M; there are people (Ganesh, for example) where that would be just about an ideal configuration.

And that’s enough talk about throttling. I’ve obsessed about this issue for much of the past two months, with solutions/workarounds that seemed to come and go. As you can imagine, ultimately determining that a reboot usually fixes the problem is less than satisfying from a troubleshooting perspective, but it’s far better than living with throttling. And the good news here: with an SSD the time it takes to reboot is only about 20 seconds.

As a final comment (and this is being written at 4AM), I spent the whole day and much of yesterday working on one of the XPS 15 laptops finishing this review. I ran some benchmarks, I had Chrome and Firefox running with dozens of tabs open, and I even loaded up a few games. That's all besides editing some images, downloading files, etc. I just reran the GRID 2 benchmark after all of that, and there was no throttling, so this isn't even something that would necessarily crop up daily. Still, it has happened in the past and I assume it will happen again. If Dell can provide a definitive fix for this issue, I’ll revisit this topic and make sure to let you know.

Dell XPS 15: General Performance

With all the talk of potential throttling, some of you might be concerned with general performance – and again, let me reiterate that a reboot appears to clear the problem, so hopefully Dell’s engineering time can track down the root cause in the coming days/weeks and fix it. Even if they can’t/don’t, the reality is that in most cases the throttling is a complete non-issue. PCMark and other tests that hit the CPU never showed any problems, and even most of the other graphics testing that I ran didn’t have problems. Of course, with a reboot apparently being a workaround, that’s not too surprising.

As you would expect from the hardware, the high-end model of the XPS 15 that we’re testing runs plenty fast and should satisfy anyone short of extreme performance types. If you want more CPU power in a laptop, you’ll basically need to get something quite a bit thicker and heavier, and even then the top model i7-4930MX/4940MX are only about 25% faster in practice (4.0GHz maximum Turbo Boost vs. 3.2GHz). The 512GB SSD also helps keep things running smoothly, 16GB RAM should be sufficient for quite some time (outside of perhaps running lots of VMs or a few other specific workloads), and when needed the GT 750M is waiting in the background to help with graphics/compute tasks. Here’s a look at our general performance testing results, which have been updated to use the latest versions of 3DMark11, 3DMark (2013), PCMark7, and PCMark8 along with Cinebench 11.5 and x264 HD 5. PCMark8 v2 scores are not (entirely) comparable with the earlier release, so for now we only have this one system tested, but that will change in time.

PCMark 7 (2013)

Cinebench R11.5 - Single-Threaded Benchmark

Cinebench R11.5 - Multi-Threaded Benchmark

x264 HD 5.x

x264 HD 5.x

Futuremark 3DMark (2013)

Futuremark 3DMark (2013)

Futuremark 3DMark 11

There’s really not much to say about overall performance. The new Dell XPS 15 may not be the absolute fastest laptop around, but it’s certainly a capable offering that can handle any reasonable load most users might want to run. If you need more performance, you likely knew before even looking at these graphs that that would be the case. As a premium consumer/business laptop, I know plenty of people that would be quite please to have one of these to tote around.

Dell XPS 15: Gaming Performance

With that lengthy preface about throttling, let’s just make it clear that all of the benchmark results here are from post-reboot testing, so throttling should not be present. What we find is that the GT 750M is a reasonable mainstream mobile GPU that can easily handle our “Value” settings and outside of the most demanding titles (e.g. Metro: Last Light) it can run our “Mainstream” settings as well. Not surprisingly, “Enthusiast” quality is mostly out of the question, except with older and/or less demanding titles. As for gaming at the native 3200x1800 resolution, that’s generally more than you can hope to get out of the GT 750M. Some games will certainly break 30 FPS at low to moderate settings, but in most cases opting for a lower resolution with higher quality settings will provide the better experience.

I also want to make note here that with 2014, we’re going to be reducing the number of games we test in our laptop reviews. There’s a real concern that running too many GPU-centric tests can distract from the overall target market for a device. While I’ve gone ahead and included most of the games from our 2013 test suite in Mobile Bench, moving forward we have decided to focus on just four games. Our current list consists of Bioshock Infinite, GRID 2, Metro: Last Light, and StarCraft II: Heart of the Swarm. These should provide a sufficient amount of data that we’ll be able to say how well a system handles gaming workloads. In some reviews we will also include other titles (e.g. if there’s a new GPU that warrants additional investigative work), including some less demanding games that will better illustrate the “casual gaming” aspect.

Bioshock Infinite - Mainstream

GRID 2 - Mainstream

Metro: Last Light - Mainstream

StarCraft II: Heart of the Swarm - Mainstream

Considering this isn’t really being targeted at a gaming audience – Dell has their Alienware brand if that’s what you’re after – the XPS 15 still manages to hold its own in the gaming tests. Throttling concerns aside, when the fans and GPU are running as expected, gaming at one fourth the native resolution and high detail settings is easily accomplished, and even 1080p medium/high detail is possible.

Dell XPS 15: Battery Life

Our final set of tests is for battery life, and here again we have a change or two to make. I did run our 2013 battery tests, but for 2014 I’ve made some changes. First, our “Heavy” test will now use the Windows Video app to play back a 1080p MP4 movie – the use of MKV files basically resulted in lower battery life by a fairly large margin, and MP4 files are readily available. I’m also considering dumping the “Moderate” workload and just sticking with Light and Heavy testing, as well as including approximate gaming battery life. There’s this mentality of “more information is always better”, but by the same token more information and testing means more time and thus less timely reviews. In general, our Medium battery life results have been pretty consistent about falling half way between our Light and Heavy tests, and with the newly modified Heavy test it’s just one extra benchmark with questionable value.

With that said, we continue to test with LCD backlighting set to 200 nits, WiFi is enabled, and earbuds are connected to the headphone jack. For the XPS 15 QHD+ display, 200 nits ended up being at exactly 50% brightness, which makes things easy on us. I do like that Dell has relatively consistent steps between backlight levels of around 35 nits per 10%. Many laptops that I’ve used in the past have been far less granular, sometimes going from 300 nits at 100% to 200 nits at 90% and then 10 nits intervals from there down to 0%.

Battery Life 2013 - Light

Battery Life 2013 - Medium

Battery Life 2013 - Heavy

Battery Life 2013 - Light Normalized

Battery Life 2013 - Medium Normalized

Battery Life 2013 - Heavy Normalized

Thanks in a large part to the 91Wh battery, the XPS 15 is able to place quite far up our battery life charts in terms of raw unplugged time. It’s not quite so awesome when we look at the normalized Min/Wh figures, but while that can be useful information at the end of the day people are going to be using the battery they get with this laptop. We measured nine hours of battery life in our light workload, nearly 6.5 hours in our moderate workload, and around 4.5 hours in our heavy workload.

Interestingly, our new Heavy test using the Video app with a lower bitrate 1080p MP4 results in battery life that’s basically the same as our previous Medium testing – so with Video, playing a fullscreen MP4 while streaming 1MBps and loading Internet pages every ten seconds isn’t really any more taxing than playing back an MP3 while surfing the web. It appears Microsoft's Video app can scale content without incurring a power penalty, whereas when I was using Media Player Classic previously higher resolution displays often did worse (e.g. look at the XPS 15 results above).

Trying to game off the mains is a different matter, however, and even with a relatively large battery the XPS 15 only manages less than two hours while running Skyrim. (If you’re wondering, for testing gaming battery life, we use the Balanced power profile with the GPU set to “Prefer Maximum Performance”. Then we load up our Skyrim save in the town of Whiterun and let the system run until the battery is drained. The camera begins to pan around the character so it’s at least moderately demanding, though other games are certainly more so.)

Dell XPS 15 Conclusion: Almost There

At the end of the day, what can be said about the XPS 15 is that it’s a great looking laptop and on paper it checks all the right boxes. In practice, I’ll be frank and state that it’s been a bit of a love/hate relationship with the XPS 15, but the hate comes more from being frustrated by my inability to get consistent results. If the system always throttled (which is what happened with the previous generation Ivy Bridge XPS 15), it would be easy to point out the problem, but that’s not the case. When it runs as it ought to, the XPS 15 offers a great blend of style, build quality, performance, battery life...and let’s not forget the awesome QHD+ display. The applications on Windows may still have issues with High-DPI right now, but long-term I’d rather have a high quality display than not, and the XPS 15 gives me exactly that.

This review is possibly one of the longest of my career, at least in terms of finishing and posting it. Originally I had planned to get the review posted ASAP, but when I started encountering issues with the GPU clocks I spent a lot of time trying to figure out what precisely was going on. I really like the laptop in general, and if I hadn’t been pounding on the system specifically running benchmarks and games and checking for throttling, maybe I could have missed that. Even with that particular issue cropping up from time to time, I still like the XPS 15 more than the vast majority of laptops I’ve tested. There was a time when performance mattered more, but these days the keyboard, touchpad, screen, and overall design end up being far more important to me, and I suspect that’s true for many of our readers.

Since the first XPS 15 rolled out several years back, Dell has clearly been trying to create a laptop – and a line of laptops – that offers a premium experience. Each generation has improved, sometimes in small ways and sometimes not. This round, the optical drive has been kicked to the curb, making way for a slimmer and lighter laptop that doesn’t have to sacrifice on battery life or performance. Everything seems to be in place for the XPS 15 to succeed, and if I were personally in the market for a new laptop the XPS 15 would certainly be high up on my list. It’s just that one item of inconsistent GPU performance that gives me pause.

If you don't care about gaming but like everything else on top, the Haswell XPS 15 a great laptop and I could easily give it an Editors' Choice award. On the other hand, until/unless the need to reboot on occasion to fix the GPU and CPU temperatures (and the resultant throttling) is addressed, those who occasionally/frequently play games might be better off waiting or looking at other options. There are quite a few laptops coming out with high-DPI displays, and some may be able to top the XPS 15. Others may be lacking in the style or build quality departments but should come with lower pricing (and a caching SSD at best). Even If Dell can fix the need to reboot on occasion to get the GPU running where it ought to be, this is a premium quality laptop with a premium price, so it’s not for everyone; it is however one of a very few options that can even think of challenging the MacBook Pro Retina.

As far as competitors go, it’s pretty simple really: if you want to run OS X, get a MacBook, but if you’re happier running Windows I don’t see much point in going that route. There really aren’t many other laptops in the same bracket right now. Razer’s Blade (and Blade Pro) is close in many ways, but it has much more of a gaming slant and a higher price tag to go with it. Otherwise, you can either wait for the upcoming spring refresh of notebooks, or you can look at some of the Ultrabooks that skip the discrete GPU entirely – Toshiba’s KIRAbook and Samsung’s ATIV Book 9 Plus might be a couple to consider. Last year’s ASUS UX51VZ is another great candidate, but it needs a refresh to Haswell (and GeForce 800M perhaps?) now. In other words, there’s very little in the way of direct competition at present.

The bottom line is that this is a laptop that has style, battery life, build quality, input devices that work well, a high-end QHD+ display, and the option for a 512GB SSD, 16GB RAM, and a discrete GPU. Fix the thermals, whatever the cause – or maybe go with Crystalwell and forego the discrete GPU – and this laptop would be golden. Instead I’m left in the uncomfortable position of really liking a laptop that has a potentially serious fly in the ointment. Hopefully we can clear that up in the coming weeks.

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