Over the past few months, we’ve covered several gaming-oriented monitors capable of refresh rates greater than 60 Hz. They all performed extremely well, and certainly lived up to their speedy specifications. But there was one thing still lacking: higher resolutions.
In the current market, a high-refresh gaming monitor is always based on a TN panel with a 6-bit/FRC color depth and FHD resolution. The speed issue is addressed decisively. Moreover, the screens that have come through our lab performed well with regards to color accuracy. However, enthusiasts plead for the greater pixel density of QHD and the superior viewing angles of IPS technology.
So far, the only company to answer that call with a quality-controlled and warrantied product is Overlord Computer, a small firm that markets gaming accessories and peripherals.
| Panel Type | AH-IPS |
|---|---|
| Backlight | W-LED, edge array |
| Screen Size | 27-inch |
| Max Resolution | 2560x1440 |
| Max Refresh Rate | 60 Hz, up to 120 Hz |
| Aspect Ratio | 16:9 |
| Native Color Depth | 8-bit |
| Native Gamut | sRGB |
| Response Time (GTG) | 6 ms |
| Brightness | 380 cd/m2 |
| Speakers | 2 x 10 W |
| VGA | - |
| DVI | 1 |
| DisplayPort v1.2 | - |
| HDMI 1.4 | - |
| Audio In | 1 x 3.5 mm |
| Headphone | - |
| USB | - |
| Media Card Reader | - |
| Panel Dimensions WxHxD w/base | 25.25 x 19 x 8.5 in 636 x 479 x 214 mm |
| Panel Thickness | 2.5 in / 63 mm |
| Bezel Width | .95-1.55 in / 24-39 mm |
| Weight | 15 lbs / 6.8 kg |
| Warranty | One year |
Overlord’s best-selling line of monitors is the Tempest series. For gamers seeking the extra size and pixel density of a 27-inch QHD display, there are several different models available. You can have one with or without an anti-glare layer, for instance. Removing that layer improves clarity and detail rendering. If you can manage the light sources in your room, it’s a compelling option.
Of course, this company's main attraction is its overclockable panels. Right now, the Tempest is the only IPS screen capable of refresh rates higher than 60 Hz. And its pricing is significantly below the average for even run-of-the-mill QHD monitors. In fact, the only less-expensive ones we know of are the gray-market Auria and Catleap screens. Neither of those run above 60 Hz reliably, though.
The key to Overlord’s success with the X270OC is a custom-made control board. That single component is the reason other IPS screens are stuck at 60 Hz. You can perform the same software tweaks necessary to run at 120 Hz on other monitors, but unless the board is equipped to handle those extra frames, you'll likely see either an unusable image or nothing at all.
The Tempest monitors are essentially hand-built using an A-grade LG panel as their core part. The proprietary control boards are tested before installation to be sure they can handle higher rate signals. Heat is minimized in the chassis by utilizing external power supplies. And the end result is the only 2560x1440 monitor available able to run at 120 Hz.
Otherwise, the X270OC is a very typical 8-bit sRGB IPS QHD monitor with a W-LED edge backlight. It runs your Windows apps, games, and other software no differently than any other display. Our press sample was tested to 120 Hz prior to shipment, and we verified its operation with our test platform. But this is no one-trick pony. We discovered it performs well in other areas too. Let’s take a look.
Our press sample arrived double-boxed with bubble wrap around the inner carton. Protecting the contents is plenty of rigid Styrofoam. Mail-order buyers have no cause for concern, as Overlord’s packaging is more than up to the task of surviving shipment.
The Tempest X270OC comes with everything you need for a quick connection and immediate action.

DVI is the only input option, so a 28 AWG cable is included. Overlord will substitute a heavier 24 AWG cable for an extra 10 bucks. It’s recommended for running at high refresh rates, and what came with our press sample. The power supply is a separate brick that accepts a standard IEC power cord, which also comes bundled. To drive the built-in speakers, a 3.5 mm audio cable rounds out the package.
The only printed materials in the box are a quick setup guide and warranty card. The user’s manual can be downloaded from Overlord’s website.
Product 360
To realize maximum image clarity, Overlord removed the anti-glare layer from our sample X270OC. Based on your room's light sources, you must take care to prevent reflections. But the extra detail and on-screen pop are well worth the trade. Our reference display for clarity comparisons is Planar's PXL2790MW. The Tempest comes awfully close to matching that excellent product. Whether you’re gaming or working in Windows, you're treated to a good-looking picture.
The bezel is a bit wide at one inch around the top and sides, and 1.5 inches across the bottom. Aside from a trim strip on the bottom with texture molded into it, the chassis is finished in a shiny black plastic. The Overlord logo on our sample wasn’t as white as the one in the photo; it was more of a medium gray. The power LED is bright blue and can’t be dimmed. If you play in the dark, its glare might be distracting.

In the lower-right corner are the control buttons. From left to right, you have brightness up/down, volume up/down, and power. The keys make a firm click when pressed, and the LED flashes to let you know something is happening. Since there’s no OSD, you won’t see any indication on the screen.

The base and upright come disassembled; you have to screw them together with the included hardware. They are finished in a medium-satin plastic.

The X270OC offers a complete set of ergonomic adjustments. You get five inches of height, 25 degrees tilt, and 120 degrees of swivel. You can also rotate to portrait mode. This is the only aspect of the Tempest that feels lower-quality. The hardware that facilitates height adjustment has some play that makes moving the panel a little wobbly. It stays solidly in-place after making changes, but it’s tricky to position the screen just the way you want. Considering how well the display performs, my critique is fairly minor.

At 2.5 inches-thick, the Tempest is beefier than average. There are no USB ports or media card readers built into the chassis. After all, gaming is the target market, and anything not needed for that purpose is excluded. A headphone jack is really the only entertainment-oriented feature we missed.

It’s hard to see in the photo, but there is plenty of ventilation at the top of the panel and around the bulge. This monitor runs cool, since its power supply is external. Removing the upright exposes a 100 mm VESA mount.
The lower vents on the bulge cover two 10 W speakers, and they're the best we've ever heard from a computer monitor. A little extra size and power translate into more bass with highs that aren't too shrill. Your own discrete surround system is naturally going to sound better. Still, we want to recognize Overlord for enabling integrated audio that stands above the rest.

There is only one way to connect the Tempest X270OC to your PC, and that’s by dual-link DVI. Use the audio input if you plan to lean on the internal speakers; DVI only carries video data. The DIN connector at the top is for the power supply. All of the jacks face sideways and are easy to find by feel. Our only concern is that the DVI input sits close to the back panel. If your cable has a bulky connector, it will be a tight fit.
The Tempest has no OSD, so the only way to calibrate it is with LUT-generating software like CalMAN. We did this for the purposes of our tests, and we’ll explain how it affects the results as we go. If you don’t have the necessary gear, Overlord at least offers color profiles to download.
Of course, the real reason you'd make the X270OC a centerpiece of your gaming PC is its overclocking ability. Natively, we're dealing with a 60 Hz IPS panel. But thanks to Overlord’s custom PCB, it can run at up to 120 Hz reliably. Why do we say “up to”? According to Overlord, not every example will be stable at 120 Hz. It is possible that you’ll see artifacts like dropped frames, or you might even hear coil whine from the timing controller choke.
You won’t simply be able to plug in the X270OC and choose 120 Hz from your Windows Control Panel, either. There are a couple of steps you need to take first.
Setting The Refresh Rate
To begin, download the Pixel Clock Patch utility here for Nvidia or for AMD/ATI. All that this app does is removes the pixel clock limiter built into your video driver. It’s a quick operation, which can be easily undone since a backup of your un-patched driver is automatically created.
Next, you need the Custom Resolution Utility. This is where you create custom refresh rates.

The first screen manages your custom configurations. To create a new one, click Add under Detailed resolutions. Then, you're taken to the manual setup window.

As you can see, there are quite a few parameters to address when overclocking a monitor. The screenshot above represents our particular X270OC. These settings may not work for everyone. But they'll suffice as a starting point. Additionally, there are plenty of online resources available to help you create custom resolutions and achieve a stable overclock.
Calibration
The only image control available is brightness, which moves in fairly coarse steps of about 8 cd/m2 per click. To complete our benchmarks, we used CalPC to generate a software look-up table after measuring the X270OC’s default state. For more information on the CalPC process, please refer to Do It Like Tom's: Calibrating Your Monitor With CalMAN RGB,where you’ll find a step-by-step guide.
To measure and calibrate monitors, we use an i1Pro spectrophotometer, a SpectraCal C6 colorimeter, and version 5.2.0.1374 of SpectraCal’s CalMAN software.
The i1Pro is very accurate and consistent measuring color on all types of displays, regardless of the backlight technology used. When we just need a luminance value, the C6 works better, especially in low light.
|
|
|
|
|
|
|
For patterns, we employ AccuPel DVG-5000 and DVDO AVLab TPG video signal generators. This approach removes video cards and drivers from the signal chain, allowing the display to receive true reference patterns. Connections are made via HDMI.

The AccuPel DVG-5000 is capable of generating all types of video signals at any resolution and refresh rate up to 1920x1080 at 60 Hz. It can also display motion patterns to evaluate a monitor's video processing capabilities, with 3D patterns available in every format. This allows us to measure color and grayscale performance, crosstalk, and ghosting in 3D content via the 3D glasses.
The DVDO generator is a new addition to our lab. It supports resolutions up to 4096x2160. We’re using it to verify the proper signal handling of QHD and UHD displays.
The i1Pro or C6 is placed at the center of the screen (unless we’re measuring uniformity) and sealed against it to block out any ambient light. The AccuPel pattern generator (bottom-left) is controlled via USB by CalMAN, which is running on the Dell XPS laptop on the right.
Our version of CalMAN Ultimate allows me to design all of the screens and workflows to best suit the purpose at hand. To that end, I’ve created a display review workflow from scratch. This way, we can be sure and collect all the necessary data with a concise and efficient set of measurements.

The charts show us the RGB levels, gamma response, and Delta E error for every brightness point from zero to 100 percent. In the table, we get raw data for each measurement. And the area in the upper-left tells us luminance, average gamma, Delta E, and contrast ratio. The individual charts can be copied to the Windows clipboard to easily create graphics for our reviews.

Every primary and secondary color is measured at 20-, 40-, 60-, 80-, and 100-percent saturation. The color saturation level is simply the distance from the white point on the CIE chart. You can see the targets moving out from white in a straight line. The further a point is from center, the greater the saturation until you hit 100 percent at the edge of the gamut triangle. This shows us the display’s response at a cross-section of color points. Many monitors score well when only the 100-percent saturations are measured. Hitting the targets at the lower saturations is more difficult, and factors into our average Delta E value (which explains why our Delta E values are sometimes higher than those reported by other publications).
The X270OC would not accept a signal from our AccuPel signal generator, so all measurements were taken with Overlord's monitor connected to a PC via DVI. Patterns were rendered by CalPC Client 3. We took default readings with all look-up tables turned off to be sure we were recording raw values. After creating a custom LUT with CalPC, we measured the results.
|
|
|
|
|
| Read the Review | Read the Review | Read the Review | Read the Review | Read the Review |
|
|
|
|
|
|
Uncalibrated
Before calibrating any panel, we measure zero and 100-percent signals at both ends of the brightness range. This shows us how contrast is affected at the extremes of a monitor's luminance capability. The X270OC does not have a contrast control, so signal clipping is not an issue. Light output can only be modulated using brightness, which affects the backlight level.
Today’s comparison group consists of the high-refresh gaming monitors we’ve reviewed, plus Asus' value-oriented 4K display, the PB287Q. I'm also adding a typical 27-inch IPS screen, NEC’s EA274WMi.

Overlord rates the X270OC at 380 cd/m2. The most light we measured was 258.5601 cd/m2, though. It's probable that Overlord is citing the panel part's specification. Typical gameplay doesn't require a super-bright display, so this shouldn't be a tremendous issue.

A low maximum black level beats the TN-based panels in our comparison. When I checked our database, I found that Overlord's X270OC bests almost all of the other IPS screens as well.

NEC's screen trumps the Tempest only because of its higher white level. The same is true of this group's other models. Among IPS displays, however, Overlord is at or near the top for maximum contrast.
We believe 50 cd/m2 is a practical minimum standard for screen brightness. Any lower and you risk eyestrain and fatigue. The X270OC bottoms out at 83.0312 cd/m2, which is a great light level for playing games in total darkness. As you’ll see below, black levels and contrast also hold up extremely well.

A last-place result in this test isn't a big deal when you’re talking about such low black levels. If all of the monitors were lined up in a row, it'd be a challenge to pick the darkest one.

The Tempest’s contrast remains super-consistent at all brightness levels. We’re seeing a positive trend towards better contrast performance from both TN and IPS screens. That Overlord can offer results this good with a $450 display is impressive.
After Calibration
Since we consider 200 cd/m2 to be an ideal point for peak output, we calibrate all of our test monitors to that value. In a room with some ambient light (like an office), this brightness level provides a sharp, punchy image with maximum detail and minimum eye fatigue. On many monitors, it’s also the sweet spot for gamma and grayscale tracking, which we'll look at on the next page. Many professionals prefer a 120 cd/m2 calibration in darker rooms. We find that makes little to no difference on the calibrated black level and contrast measurements.
We set the maximum output level using the X270OC’s only available adjustment, brightness. Our results reflect the color and gamma adjustments made by the CalPC-generated LUT.

A calibrated black level result of .218 cd/m2 is excellent. Typically, monitors take a small hit after we adjust them. But not the Tempest. Perhaps this is attributable to the finer control possible with a software LUT. Most displays employ OSD controls that aren't as precise.
An improvement like this makes calibration worth the time and expense, though.

The X270OC posts incredibly consistent contrast results. Whether you calibrate or not, and regardless of backlight setting, the contrast ratio is always around 925 to 1.
ANSI Contrast Ratio
Another important measure of contrast is ANSI. To perform this test, a checkerboard pattern of sixteen zero and 100-percent squares is measured. We get a somewhat more real-world metric than on/off measurements because we're testing the display’s ability to simultaneously maintain both low black and full white levels, plus factoring in screen uniformity. The average of the eight full-white measurements is divided by the average of the eight full-black measurements to arrive at the ANSI result.

The Tempest loses no ground in the ANSI contrast test. Since screen uniformity is a factor, some samples will measure better or worse than ours. Even still, it's impressive to come across such strong build quality from a low-priced IPS display.
The majority of monitors, especially newer models, display excellent grayscale tracking (even at stock settings). It’s important that the color of white be consistently neutral at all light levels from darkest to brightest. Grayscale performance impacts color accuracy with regard to the secondary colors: cyan, magenta, and yellow. Since computer monitors typically have no color or tint adjustment, accurate grayscale is key.
Since we had to measure the Tempest using PC-generated patterns, we made sure to turn off any LUTs before starting.

If you simply plug in the X270OC, this is the grayscale performance you get. Green errors are visible at all brightness levels above 10 percent, and they're most obvious in document windows due to the white backgrounds. The issue isn't as bothersome in games or while watching video. Compared to a calibrated image, it does look a little flat, though.

CalPC facilitates an extremely precise calibration. Most OSDs give you, at most, 100 steps in their RGB controls. Using a LUT means all 256 levels of each color can be adjusted to achieve an essentially perfect result.
And now, back to the comparison group:

An average error of 5.9 Delta E is high for any monitor. In the X270OC’s case, the values range from 2.6 to 7.6.

That the Tempest doesn’t finish first with its LUT calibration is a testament to BenQ’s XL2720Z, more than anything. A result of .49 Delta E reflects a really low grayscale error.
Gamma Response
Gamma is the measurement of luminance levels at every step in the brightness range from 0 to 100 percent. It's important because poor gamma can either crush detail at various points or wash it out, making the entire picture appear flat and dull. Correct gamma produces a more three-dimensional image, with a greater sense of depth and realism. Meanwhile, incorrect gamma can negatively affect image quality, even in monitors with high contrast ratios.
In the charts below, the yellow line represents 2.2, which is the most widely used standard for television, film, and computer graphics production. The closer the white measurement trace comes to 2.2, the better.

We’re only showing one gamma chart because it corresponds to the un-calibrated and calibrated state of Overlord's X270OC. CalPC didn’t need to make any changes. The miniscule hump at 90 percent represents only a 1.4 cd/m2 aberration; it's completely invisible.
Here is our comparison group again:

The Tempest has the flattest gamma tracking in the group, right out of its box. That's particularly important in games, where you want to be sure you’re seeing every tiny detail.
We calculate gamma deviation by simply expressing the difference from 2.2 as a percentage.

Only that tiny error at 90 percent prevents the Tempest from posting a perfect gamma result. Again, you won’t be able to see anything wrong. Detail rendering on this monitor is as good as it gets.
Color gamut is measured using a saturation sweep that samples the six main colors (red, green, blue, cyan, magenta, and yellow) at five saturation levels (20, 40, 60, 80, and 100%), providing a realistic view of color accuracy.

We like the un-calibrated chroma results better than the grayscale ones. Aside from an oversaturated blue primary, most points come fairly close to their targets. You can see a little under-saturation happening in red, but it’s not egregious. Luminance is properly used to compensate for the CIE chart errors. It'd only take a couple of tweaks to the RGB sliders, if there were any, to improve this.

CalPC turns average color into perfection with its custom LUT. We just can’t get measurements like this out of an OSD-based setup. Comparisons become a little unfair, since there's equipment needed to replicate our work. But with no other way to calibrate the X270OC, we don’t have a choice.
We return to the comparison group:

Given the visual representation above, an average error of .53 Delta E is no surprise. It can’t get much better.
Gamut Volume: Adobe RGB 1998 And sRGB
There are basically two categories of displays in use today: those that conform to the sRGB/Rec. 709 standard like HDTVs, and wide-gamut panels that show as much as 100 percent of the Adobe RGB 1998 spec. We use Gamutvision to calculate the gamut volume, based on an ICC profile created from our actual measurements.

Since none of the primaries are under-saturated, CalPC nearly hits 100-percent sRGB gamut volume. If we ran this test on an un-calibrated X270OC, its volume would be around 105 percent.
The Tempest is one of the least-expensive 27-inch IPS screens available. Even though it’s a gamer-oriented screen, it could work well in a photo-editing environment, so long as the wider Adobe RGB gamut isn't needed and you perform a software LUT calibration.
The more monitors we test, the more we can see that off-axis viewing performance is dependent not only on pixel structure (IPS, PLS, TN, etc.) but the backlight technology as well. And we can see that the anti-glare layer makes a difference too.

Since we couldn’t use the AccuPel, we replaced our Windows desktop with a gray step pattern. You can see the clear advantage that IPS technology enjoys compared to the other TN-based ones we've reviewed. The view from 45 degrees to the side only shows a little light falloff and no color shift. From above (also 45 degrees), there is a tendency toward green and red, depending on the brightness level. Overall though, you won’t find off-axis image quality like this on any high-refresh TN display.
Screen Uniformity: Luminance
To measure screen uniformity, zero and 100-percent full-field patterns are used, and nine points are sampled. First, we establish a baseline measurement at the center of each screen. Then the surrounding eight points are measured. Their values get expressed as a percentage of the baseline, either above or below. This number is averaged.
It is important to remember that we only test the review sample each vendor sends us. Other examples of the same monitor can measure differently.
First up is black field uniformity.

One of the biggest complaints about entry-level IPS displays is poor black field uniformity, better known on Internet forums as light bleed. Happily, our sample does not suffer from this malady. In fact, it looks just as good as any other monitor we’ve tested, regardless of price. Measurements show slightly hotter zones across the bottom of the screen.
Here’s the white field result:

A measurement of 3.71 percent means the Tempest has near-perfect white uniformity. We couldn’t see any areas that were brighter or dimmer than the rest.
Screen Uniformity: Color
To measure color uniformity, we display an 80-percent white field and measure the Delta E error of the same nine points on the screen. Then we simply subtract the lowest value from the highest to arrive at the result. A smaller number means a display is more uniform. Any value below three means a variation that is invisible to the naked eye.

Although the X270OC finishes last in our test group, its color deviation across the screen is still invisible. To see good quality-control at such a low price gives us hope that IPS monitors will all become less expensive soon.
To perform these tests, we use a high-speed camera that shoots at 1000 frames per second. Analyzing the video frame-by-frame allows us to observe the exact time it takes to go from a zero-percent signal to a 100% white field.
We had to do things differently for this review since our pattern generator maxes out at 60 Hz. So, we filmed a mouse movement that triggers the field pattern’s appearance. Since this is less precise than using the generator, we averaged five measurements.
Here is the screen draw result:

At 120 Hz, the draw time is about two-thirds faster than a typical IPS panel’s time of 25 milliseconds. Needless to say, the reduction in motion blur is more than subtle. We ran through many of the tests at blurbusters.com and saw clear improvements in all of them when running at 120 Hz versus 60.
Here are the lag results:

All of the high-refresh displays we’ve tested, including the Tempest, demonstrate extremely low input lag. Consider the advantages enjoyed by the AOC, BenQ, and Asus VG248QE. They employ TN panels with 6-bit/FRC color depth. And they’re only driving a resolution of 1920x1080. The Tempest is IPS. It’s a full 8-bit panel. And it’s refreshing 44 percent more pixels. Now that’s impressive. A price tag of $450 is just icing on the cake.
At $450, the Tempest X270OC satisfies my value benchmark, if only because it's an overclockable IPS-based monitor. We've already established the advantages of running at 120 or 144 Hz in previous gaming monitor reviews. And, like you, we've lamented the fact that all other high-speed displays make certain compromises with TN technology, 6-bit/FRC color, and FHD resolutions. Now it seems that Overlord is breaking new ground, and we hope it inspires other companies to follow suit.
It seems like every time I review a QHD monitor, the audience reaction is that it’s too expensive and too slow. I'd agree with this assessment, for the most part. Now that LG’s IPS panels are at the heart of nearly every 27-inch QHD monitor on the planet, we side with the majority of enthusiasts impatient for prices to fall. Over the past 18 months, these displays were stuck at $600 and higher. There is some relief to be had in gray-market Korean products, but when you go off-trail to buy a monitor, quality becomes less consistent. Sometimes the prudent decision is to pay extra for support, a usable warranty, and a reasonable assurance that the panel you buy is free of defects.
Thanks to Overlord, we can now choose high quality and high performance. With its more robust control board installed, any user can overclock their Tempest X270OC simply by activating a few software tweaks. The utilities provided online make it easy to patch your Nvidia or AMD drivers and create custom display timings. With a little help from Overlord’s tech, I was able to get my sample running perfectly at 120 Hz in a few minutes.
If you’re concerned about stability, you needn’t be. I installed the Tempest and used it for several weeks for productivity and gaming, running at 120 Hz the entire time. There was nary a hiccup and I thoroughly enjoyed the smoother motion that comes with doubling the standard refresh rate. Activities as mundane as moving the mouse cursor across Windows' desktop are more satisfying. We’ve become so accustomed to the blur inherent in LCD panels that it’s easy to forget what judder-free motion even looks like.
Before I conclude, I have one final bit of advice for anyone considering the Tempest X270OC as a centerpiece of their gaming rig. And it's the same guidance I’d offer with any high-refresh rate monitor. To maximize your experience, buy as much graphics processing horsepower as you can afford. Since you'll save quite a bit on the display, put more budget into a capable video card. Gaming at a native 2560x1440 (and beyond) is taxing. If you skimp at any point before the signal leaves your computer case, you won't get as much enjoyment from the Tempest in your favorite titles. Feel free to consult Best Graphics Cards For The Money for help choosing an appropriate GPU.

At least now you can push those extra pixels without buying a monitor that costs as much as your whole system. For its exceptional performance and value, we’re giving the Overlord Tempest X270OC the Tom’s Hardware Smart Buy award.


