Cooler Master Tempest GP27U Monitor Review

The Cooler Master GP27U has a rather simple design with a hexagonal stand. It's mainly black with a bit of lighting in the back.

The build quality is okay. The plastic materials feel cheap and flex easily. The cable management clip also comes off easily. Luckily, the base of the stand is aluminum and feels solid, but there's still wobble if you have the monitor on an unstable desk.

Like many people have reported online, the edges of the screen don't appear properly if you are looking at a tight angle or if you're looking at the screen from an extremely close distance. It's common for monitors, but the issue seems to be worse with this one. However, it isn't a problem if you're sitting at a normal distance.

The Cooler Master GP27U has excellent ergonomics, as it's easy to adjust to an ideal position. The stand also offers basic cable management through a clip, but the clip comes off easily if you pull the cables.

The base of the stand is aluminum and has a hexagonal shape. Because it takes up a lot of space, you need a big desk if you want space for your keyboard and mouse in front.

There's a joystick on the back right side to control the on-screen display or power it off.

• Power supply and cable
• HDMI cable
• DisplayPort cable
• USB-B to USB-A cable
• USB-C to USB-C cable
• User documentation and guides

The Cooler Master GP27U has an alright native contrast ratio. It's mainly limited by its IPS panel, which has low native contrast, but the full-array Mini LED local dimming feature helps further improve it. Exceptionally, we also measured the contrast using the TV Test Bench 1.9 methodology, which uses a real scene photo instead, as you can see here. You can see the results of that below:

• Contrast: 69,867:1
• Local Contrast: 2,525:1

The Contrast uses the average black levels of the four black corners, while the Local Contrast is the contrast between the white and black levels closer to the cave. However, these numbers aren't comparable to the results in the review because they're tested differently, and the local dimming interacts with the checkerboard pattern differently than real content. In this case, it can effectively turn off the dimming zones in the four corners of the cave scene, but it can't do that with the black squares around the center white square in the checkerboard. That said, if you prefer something with a near-infinite contrast that displays perfect blacks next to bright highlights, look into the Dell Alienware AW3225QF.

The Cooler Master GP27U has a decent full-array Mini LED local dimming feature. There are 576 zones, and the recommended setting is with Local Dimming on 'High', and you can enable it in SDR and HDR. It's better than any edge-lit monitor and keeps up with other Mini LED monitors like the Samsung Odyssey Neo G8 S32BG85. The screen is uniform, and the local dimming helps eliminate any backlight bleed you see with it disabled. The algorithm keeps up with fast-moving objects well, but at times, you can see that it changes zones too quickly, which can get distracting. There's minimal black crush on 'High', as you can see here, so it preserves details well, and there isn't too much blooming either. There's more black crush with the local dimming set to 'Low', and the screen isn't as bright.

The local dimming performs best when viewing from directly in front because there's a lot of blooming, and the overall image looks worse when moving off-center, meaning it isn't ideal for watching content with a friend. You can see an example of the blooming when viewing off-center here. If you want something where there isn't as much blooming when viewed from the sides, then check out the Acer ‎Predator X32 Fpbmiiiiphuzx.

Originally, you couldn't enable the local dimming at the same time as the variable refresh rate (VRR), but Cooler Master has since released a firmware 1.1 update to fix that on Nov. 25, 2022, and you can now use both at the same time. However, there's a noticeable image flicker with both on simultaneously. Even though a new 'Low Flicker' option is available in the local dimming settings with firmware 1.2 (version A) released on Feb. 17, 2023, it doesn't improve or reduce the flicker. You can read more about this in Image Flicker. Additionally, firmware 1.4.1 was released in Sep. 2023 to improve the local dimming performance in SDR, and while it makes the screen slightly brighter by a few nits, the local dimming doesn't look much different.

If you want something with more dimming zones and better local dimming performance, then check out the INNOCN 27M2V.

The SDR peak brightness is excellent, and you won't have any issues using it in a bright room. Enabling the local dimming helps make it bright, and there isn't too much distracting change in brightness between different scenes either.

These results are from after calibration in the 'Standard' Picture Mode with the Brightness at its max and Local Dimming on 'High'. It was tested with firmware 1.2 (version A), which was updated on Feb. 17, 2023, and the update made the brightness worse compared to the firmware 1.1 update released on Dec. 2, 2022. That firmware had a Real Scene brightness of 1,064 cd/m². However, the current brightness is similar to the brightness before the Dec. 2022 update.

We also measured the peak brightness with local dimming disabled, but all other settings were the same. The Real Scene brightness is 613 cd/m², and most windows are around 650 cd/m². However, the minimum brightness with local dimming disabled is 77 cd/m², which can be too bright if you want to use it in a dark room.

The HDR peak brightness is fantastic. It gets bright enough to make highlights pop and gets very bright even with larger highlights, which is great. The EOTF also follows the target well until there's a sharp roll-off at the peak brightness, causing a loss of fine details in bright scenes.

These results are with firmware 1.2 (version A), which was updated on Feb. 17, 2023. This update improves the peak brightness, especially with large-sized highlights, as the brightness before this update was around 1,000 cd/m² with most scenes.

Unfortunately, after the firmware 1.1 update on Dec. 2, 2022, the Gamma, Color Domain, and Color Space settings are locked at their defaults when in HDR, and you can't change them.

The Cooler Master GP27U has a decent horizontal viewing angle. It's fine if you have to share work with a coworker or client, but not if they need to see accurate colors, because the colors start to shift quickly. As explained in the Local Dimming section, the image looks worse in dark scenes with local dimming enabled and when viewing off-center as there's blooming.

The vertical viewing angle is good. You won't have issues using it when viewing it from above, like when you're standing up.

The gray uniformity is great. There's minimal dirty screen effect in the center, which is great for browsing the web or watching sports, but the edges are darker than the rest of the screen.

The Cooler Master GP27U has remarkable black uniformity with the local dimming feature enabled. There's minimal blooming around bright objects, and blacks look deep. You need to set Local Dimming to 'High' for the best performance, as disabling it results in a blue tint and backlight bleed.

The accuracy before calibration is alright. The white balance is noticeably off, causing the entire image to look inaccurate, and most colors are off, too. The color temperature is warmer than the 6500K target, giving the image a red tint, and gamma doesn't follow the target sRGB curve well, as most scenes are too dark.

These results are with firmware 1.1 (version A) released Dec. 2, 2022. This update locks the colors to the sRGB color space well and lets you change any setting you like while in the sRGB mode. Initially, you couldn't change the Color Temperature setting, then after the firmware 1.1 update on Nov. 25, 2022, the sRGB clamp broke, causing the sRGB coverage area to be 159.1%.

If accuracy before calibration is important for you, check out the Acer Nitro XV275K P3biipruzx, which has much better accuracy.

The accuracy after calibration is fantastic and removes nearly all inaccuracies with the white balance, color, color temperature, and gamma.

The SDR color gamut is simply outstanding. It has perfect coverage of both the commonly-used sRGB color space and the Adobe RGB color space used in some photo editing, but it oversaturates reds in that color space.

The Cooler Master GP27U has an outstanding SDR color volume. Besides perfectly dark colors, it displays all colors very well at various luminance levels.

The HDR color gamut is fantastic. It has near-perfect coverage of the common DCI-P3 color space and decent coverage of the wider Rec. 2020 color space. However, tone mapping is off with both, particularly in Rec. 2020, so there's a loss of details with saturated colors.

These results are with firmware 1.2 (version A), which was updated on Feb. 17, 2023. The update locks the Color Space to 'DCI-P3' instead of 'BT. 2020', which helps improve the tone mapping with white in DCI-P3, but some other colors are worse.

Unfortunately, after the firmware 1.1 update on Dec. 2, 2022, the Gamma, Color Domain, and Color Space settings are locked at their defaults in HDR, and you can't change them.

The HDR color volume is excellent. It displays colors at a wide range of luminance levels well, but it's limited by its incomplete color gamut. These results are with firmware 1.2 (version A) that was updated on Feb. 17, 2023, which slightly improves the color volume, but not significantly.

The Cooler Master GP27U has decent reflection handling. Although it struggles to reduce distracting reflections from some strong light sources, it still gets bright enough to fight even intense glare.

Thanks to the high resolution and high pixel density, the text clarity is incredible. Enabling Windows ClearType (top photo) helps improve the clarity of certain letters, but you likely won't need it anyways. These pictures are with Windows 10, and you can see what it looks like with Windows 11:

• ClearType On
• ClearType Off

The gradient handling is fantastic. You won't see banding between shades of the same color, like in a sunset.

To achieve the max refresh rate over DisplayPort, you'll need to update the firmware because, initially, you couldn't reach 160Hz over DisplayPort. Cooler Master released an update for firmware 1.1 on Nov. 25, 2022 to fix that.

Although the Cooler Master GP27U isn't certified by either NVIDIA or AMD, its VRR support works both with AMD and NVIDIA graphics cards. It also supports Low Framerate Compensation for the VRR to continue working even when the frame rate drops too low. It also works with G-SYNC and FreeSync over HDMI and DisplayPort across its entire refresh rate range.

Originally, you couldn't enable the local dimming at the same time as VRR, but after the firmware 1.1 update on Nov. 25, 2022, you can now do that. VRR and HDR are supported at the same time. That said, if you prefer something that doesn't have any issues with VRR and HDR without any firmware updates, then look into the LG 27GR95UM-B.

The response time at its max refresh rate of 160Hz is fantastic. There's minimal motion blur, and fast-moving objects look incredible. There are various overdrive settings, including a custom one called 'User', that you can adjust from 0 to 100. Setting it to '30' is the recommended setting at its max refresh rate if you're going to use the mode, but the 'Normal' setting still has a faster response time with less overshoot. It's unclear what exactly the 'Dynamic' mode does, but it performs like 'Advanced'.

The response time at 120Hz is once again fantastic. However, it's better to leave the overdrive setting to 'Off' because the other settings have too much overshoot. Setting the 'User' mode to '15' actually performs a lot like 'Off', but it has a slightly slower response time.

The response time at 60Hz remains excellent, as long as you leave the overdrive setting disabled as the other settings have more overshoot, including 'User'.

The Cooler Master GP27U doesn't have an optional backlight strobing feature to reduce persistence blur.

The Cooler Master GP27U is flicker-free when you have local dimming disabled, which helps reduce eye strain. However, the backlight flickers using pulse-width modulation once you enable the local dimming, but it's a high frequency. You can see the graph for it here.

Unfortunately, there's a noticeable image flicker with local dimming and VRR enabled. This only happens in this situation, and it disappears with local dimming off. Even after Cooler Master added a new 'Low Flicker' option in the local dimming settings with the firmware 1.2 (version A) update released on Feb. 17, 2023, the flicker is still there. You can see examples of it below with the different firmware.

The Cooler Master GP27U has low input lag for a responsive feel, and you won't notice any delay. The posted results are with local dimming disabled, but we also took extra measurements with it enabled and found that it adds about 0.2ms, which is negligible.

The Cooler Master GP27U works well with the PS5 as it has HDMI 2.1 bandwidth, allowing you to take full advantage of the PS5. It originally worked without issue after the monitor's release, but a firmware 1.1 update on Nov. 25, 2022, broke the PS5 support as 4k no longer worked. However, Cooler Master released another firmware 1.1 update on Dec. 2, and there aren't any problems with the console.

The monitor works with any signal from the Xbox Series X, and unlike with the PS5, there aren't any issues with any of the firmware updates.

The DisplayPort Alt Mode with the USB-C input lets you display an image from a compatible laptop, and the 90 W of power delivery is enough to charge even most laptops while you're using it.

The Cooler Master GP27U works well with M1 MacBooks. The VRR and HDR work well and you can close the laptop's lid while working on the monitor as long as you're using the USB-C connection. Windows return to their original position when opening the lid, too. You also need to make sure you have the KVM settings enabled for everything to work.

The Cooler Master GP27U has a few extra features, including:

• Black Stabilization: Adjusts gamma to make it easier to spot players in dark scenes.
• Blue Light Filter: Removes blue light to help reduce eye strain.
• Crosshair: Adds a virtual crosshair to any game that your system can't detect.
• FPS Counter: Shows the current frame rate of your source.
• Timer Adds a virtual crosshair on the screen.

Its KVM switch lets you control two devices with the same keyboard and mouse. Before firmware 1.4.1, released in Sep. 2023, some issues caused devices to disconnect after the monitor went into sleep mode. The update fixes this as you can set USB Charge to 'On', and your devices stay connected.