Gaming Performance

The Cooler Master Tempest GP27Q sports a 165 Hz refresh rate UltraSpeed IPS panel, which supports the adaptive synchronization technology from both AMD and NVIDIA graphics cards. The adaptive synchronization range is 48–165 Hz, so that's the framerate range your PC should be able to achieve at 2560x1440 resolution to experience buttery smooth, screen-tear-free gameplay. Cooler Master is awaiting official AMD FreeSync Premium certification.

Response Time and Overdrive

The response time of the Cooler Master Tempest GP27Q is specified as 1 ms GtG. The panel uses overdrive technology to make the pixel transitions faster, and you will find the option in the Gaming Setup > Overdrive menu in the OSD. Overdrive has six settings: Off, Normal, Advanced, Ultrafast, Dynamic, and User. The latter is particularly interesting, as it allows us to manually adjust the overdrive level on a scale from 0 to 100 in increments of 1.


I tested the response time with the Open Source Response Time Tool (OSRTT), developed by Andrew McDonald of TechTeamGB. It's a nifty tool that, combined with the OSRTT Launcher app, measures panel response times and presents them through detailed graphs and easy-to-read heatmaps. You can find everything you might want to know about the OSRTT in its technical documentation and on the official website, where you can order your own unit, too. The OSRTT gives us three interesting heat maps to observe.

Perceived Response Time tells us how much time the panel took to transition from one color to another. This measurement is expressed in milliseconds and includes overshoot. In other words, if the panel exceeded the target value, the perceived response time also includes the time it took for the transition to recover from overshoot and stabilize on the target value. I'm running my tests with recommended settings, so with a fixed RGB 5 tolerance level and with gamma-corrected RGB values.

RGB Overshoot tells us how much a specific transition missed the target value. For example, if the panel was transitioning from RGB 51 to RGB 204, and it initially landed on RGB 212, the overshoot RGB value is 8. Overshoot can be both positive and negative, and it commonly occurs at extreme overdrive settings when pixels are driven by high voltage. In practice, an overshoot manifests as an afterimage or a halo around a moving object. It can be easily spotted even when doing something as basic as scrolling through a webpage.

Visual Response Rating is the most abstract heatmap generated by the OSRTT Launcher; in essence, it's an ever-evolving scoring system. To quote OSRTT's technical documentation, it is a finite score rather than a direct measurement. The calculation is pretty simple; it's: "100 – (Initial Response Time + Perceived Response Time)." Since both metrics use the same tolerance level, if a display doesn't overshoot, both times will be identical. This essentially rewards displays that are fast with a small amount of overshoot over displays that aren't as fast even if they don't overshoot at all – while still overall preferring ultra-fast, accurate monitors.

Here's how the Cooler Master Tempest GP27Q fares in the pixel response time test for all six overdrive settings. We're looking for a setting that has a low measured average perceived time value and as little overshoot as possible.



As you can see by examining the numerical data and accompanying heatmaps, the best overdrive setting is Normal. It has the lowest perceived pixel transition time value and no noticeable overshoot. A close second is the Advanced setting, which I found in practice pretty much identical to Normal. You can also get some great results by setting Overdrive to User and adjusting the "slider" to 20. The Ultrafast setting comes with substantial pixel overshoot, and the Dynamic setting seems to be identical to Advanced, regardless of the framerate/refresh rate. With Overdrive set to Normal, Advanced, or User 20, the overall motion handling of the Cooler Master Tempest GP27Q is excellent.

Moving Picture Response Time (MPRT)

In the OSD's Gaming Setup menu, you'll find the MPRT toggle. If you turn it on, the backlight will start strobing to achieve a faster pixel response time at the expense of picture brightness. You're also losing the ability to use adaptive synchronization; turning MPRT on instantly deactivates FreeSync/G-SYNC. The same is true for local dimming and HDR. MPRT can be used with the refresh rate set to 120, 144, or 165 Hz.

The MPRT response time is not to be confused with GtG response time, as the commonly used GtG value tells us how much time it takes for a pixel to change between two colors. At the same time, MPRT, also known as display persistence, represents how long a pixel is continuously visible. It's important to know that MPRT isn't a blur reduction technology but a measurement that can be lowered by backlight strobing.

Activating MPRT on the Cooler Master Tempest GP27Q comes with three settings: Low, Medium, and High. In terms of achievable brightness, Low is the only viable setting, as it locks the brightness to an acceptable level of 263 cd/m². The Medium setting lowers it to 131 cd/m² and setting it to High results in actual brightness of only 66 cd/m², which is too dark even for users who prefer a darker picture. All three MPRT settings come with noticeable strobe crosstalk, so while you're making the moving images sharper, you're also introducing noticeable ghosting, which is why it's best to skip using the MPRT feature altogether.

Input Lag

To measure the input lag of a monitor, I recently switched from using the LDAT V2 (Latency Display Analysis Tool), which I've covered extensively in my NVIDIA Reflex review, to the OSRTT Tool. In a recent update, the OSRTT Tool and the accompanying software were upgraded with a DirectX code developed by Andrew McDonald of TechTeamGB, which allows the OSRTT Launcher to track the events and capture the frame time, making it possible to isolate the monitor latency from other factors that come into play when using the click-to-photon testing methodology, namely the USB polling rate and game render time. For a deeper insight, I suggest you watch an excellent overview video made by Andy himself.

While I used a consistent methodology in all my previous LDAT-based monitor reviews and kept everything the same, switching to the OSRTT-based approach isolates me from potential issues, such as game engine updates (I based my tests on Overwatch, which recently transformed into Overwatch 2), and allows me to move on to a different testing system at will. I have to admit it was becoming increasingly annoying having to keep my old Core i9-9900K/RTX 2080 Super test system around for nothing but monitor input lag testing. Thanks to Andy for his tireless work on the OSRTT Tool and the OSRTT Launcher software!

Here's how the Cooler Master Tempest GP27Q holds up in terms of input lag after doing 100 iterations of the input lag test.



The Cooler Master Tempest GP27Q shows an average input lag of around 3 milliseconds, making it a perfectly viable choice even for hardcore gaming.