720Hz on the LG 27GX790B comes from a 720p dual mode
The LG 27GX790B 720Hz Dual Mode is real, and it costs three quarters of the panel’s pixels. The monitor runs 540Hz at QHD natively. Switching to 720Hz drops it to 1280x720, so pixel density falls from about 110 PPI to about 55. That buys 180Hz more refresh.
Key Takeaways
- The 27GX790B runs 540Hz at QHD and 720Hz only at 720p.
- Turning on 720Hz throws away three quarters of the pixels.
- At 720p on a 27-inch screen you get about 55 PPI.
- Feeding 720 frames a second needs a PC almost nobody owns.
- The new OLED panel stack is the better reason to buy it.
What Dual Mode switches on the LG 27GX790B
LG sells one monitor with two personalities, and the marketing prints the faster one on the box. In its native state the 27GX790B is a 27-inch QHD panel running at 540Hz. Dual Mode is a hotkey that rebuilds the signal at 1280x720 and pushes refresh to 720Hz.
The panel is a 4th-generation Primary RGB Tandem WOLED, measured at 26.5 inches. TFTCentral’s spec breakdown puts it at 0.02ms grey-to-grey and 1500 nits peak on a small window. The video feed arrives over DisplayPort 2.1 at UHBR 13.5, and DSC compression squeezes it down enough to fit. On the HDMI side, that same bandwidth crunch is what a 96Gbps HDMI 2.2 cable exists to relieve.
| Native mode | Dual Mode | |
|---|---|---|
| Resolution | 2560x1440 | 1280x720 |
| Refresh rate | 540Hz | 720Hz |
| Total pixels | 3,686,400 | 921,600 |
| Pixel density | about 110 PPI | about 55 PPI |
| Time per frame | 1.85ms | 1.39ms |
Halving both dimensions leaves a quarter of the pixels, so you give up 75 percent of the image to shave 0.46ms off each frame. LG’s published material does not say whether the 720p signal stretches to fill the panel or shows letterboxed in the middle. Treat the on-screen result as unconfirmed until someone measures one.
What GPU do you need to hit 720 frames per second?
720Hz means the PC has to finish a new frame every 1.39 milliseconds. It has to hold that pace for a whole match, in the middle of a firefight as well as on a menu screen.
Counter-Strike 2 is the one mainstream case that clears the bar. A community benchmark on an RTX 5090 and a Ryzen 7 9800X3D recorded about 1,087 fps average at 1280x960 on low settings. An RTX 5080 with a 9950X3D managed roughly 870 fps in the same test conditions.
Those are averages. The dips underneath fall well below 720 fps, and during them the panel repeats frames because the PC has no new one ready.
Step outside that narrow slice of games and the numbers collapse. Anything with modern lighting, ray tracing, or a busy simulation layer lands in the low hundreds at any resolution. The 540Hz native mode already covers that with room left over. At four-figure frame rates the graphics card stops being the limit anyway. The CPU and the game engine set the ceiling, and cutting resolution further no longer helps. Most players can’t saturate 540Hz, and 720Hz needs even more frames than that.
The Tandem OLED stack is the bigger upgrade on this panel
Primary RGB Tandem OLED stacks separate red, green, and blue emissive layers on top of each other to make its white light, which colour filters then split into subpixels next to a white one.
Stacking lowers the current each layer carries at a given brightness, so the panel reaches higher sustained output without driving any single layer as hard. That is also the argument for slower burn-in. The 1500 nit peak and the 335 nit full-screen figure both come from that structure.
The panel keeps its white subpixel, so it does without the RGB-stripe layout LG Display builds into its newer 27-inch 4K panel, the one that cuts the coloured fringing on text. At 110 PPI it falls short of retina-class sharpness and reads like an ordinary desktop screen. Dual Mode gives that up: at 720p, this text-friendly panel looks like a 2008 laptop screen.
The 5K model in the same family handles the switch far better. On the 27GM950B, Dual Mode halves the count on both axes, so each QHD pixel lands on a clean 2 by 2 block. LG’s 32-inch 32GS95UE gets the same clean halving, dropping 4K to 1080p for its 480Hz push.
The 720Hz Dual Mode is not even the fastest one available
On Dual Mode speed alone, LG’s headline number loses to IPS monitors. DisplayNinja’s monitor tracker lists several 27-inch 1440p panels whose Dual Mode runs at 1000Hz or better, all built on cheaper panel technology than Tandem OLED.
| Monitor | Panel | Native | Dual Mode |
|---|---|---|---|
| LG 27GX790B | 26.5-inch OLED | QHD 540Hz | 720p 720Hz |
| Acer XV273U F5 | 27-inch IPS | QHD 540Hz | 720p 1000Hz |
| LG 25G590B | 24.5-inch IPS | 1080p 1000Hz | none needed |
The 25G590B is the cleanest deal of the three, because it reaches 1000Hz at its native resolution with no mode switch at all.
Who the 720Hz mode is for
The mode earns its keep for a player who competes in one title at minimum settings on a top-tier CPU and doesn’t care how anything else looks. For that person, 0.46ms saved on every frame is an edge. The same reasoning runs through the rest of the chain, where a magnetic keyboard’s 0.12 ms penalty buys adjustable actuation.
Everyone else should set QHD at 540Hz and never open the menu again. The 2026 UltraGear launch coverage put the 27GX790B at 849 euros. At that price, the OLED panel is what you’re paying for.
A Dual Mode toggle costs nothing when you leave it off, so none of this is a reason to skip the monitor. Read reviews carefully, though: a benchmark quoting 720Hz is quoting the 720p mode, and a latency figure measured there does not describe the screen you will use. Watch the software side too, since new LG monitors have started pushing McAfee pop-ups through Windows Update.
Across the whole GX7 family, pick the model by its native resolution and native refresh, from this 27-inch panel up to the 52-inch wall-format sibling.