Asus XG27ACS Review – Budget 1440p 180Hz 1ms Gaming Monitor

This is the newest addition to Asus’ ROG line of gaming monitors, the XG27ACS, a more budget-friendly 27” 1440p 180Hz Fast IPS gaming monitor with a claimed 1 millisecond response time and even “GamingAI”. Yeah, the ‘AI’ has leaked into monitors now too… Asus is undercutting everyone – including themselves – with this one coming in at an MSRP of £329, and considering the feature set, it looks like an awfully promising option – but, like, is it? Well, let’s test it and find out! 

First I want to give you a tour of some of the features this thing offers, and surprisingly even for a more budget option, this has a lot. First is arguably the most rare, albeit an option I can’t use, but that’s ELMB Sync. ELMB or “extreme low motion blur” is Asus’ name for their backlight strobing mode. Let me show you some high speed footage so you can understand what this is doing here – this will contain flashing images so be warned. With ELMB off you can see, well nothing is happening. This display is just on as normal. Now here is what ELMB looks like – it turns the backlight off for all but one millisecond per frame, which means that at 180 hertz the backlight is only on for 18% of the frame time. This means you get about one fifth of the brightness too, which makes the display noticeably dimmer. This flickering is also incredibly uncomfortable for me, so as much as it can help give you a crisper visual experience, I can’t look at it for long enough to make any use out of it. I’m also fairly convinced it isn’t great for you either, but it’s there if you want it. The special thing here though is that second word, “Sync”. That means you can enable ELMB while adaptive sync is active. This is a rarity, and so it’s pretty cool to see it available here. 

As for those “GamingAI” features, I want to make it clear that they are just marketing fluff for wholly existing features. There are no neural networks involved here – the features they list are just overdrive, a colour changing crosshair, and “shadow boost” that just ups the gamma curve. Overdrive is a rather interesting one though, see most monitors have three, four, maybe five overdrive modes to choose from. Asus decided that wasn’t good enough, and made it 20. 2-0. For those of you wondering, yes, I did use my open source response time tool to measure every single setting. It took hours. If you want to support painstaking work like this, or inflict similar suffering on yourself, I do make these tools myself, by hand, and you can buy one at OSRTT.com. As for the rest of the on-screen menu, it’s pretty well laid out and easy to navigate, with all the settings you’d expect. You’ve even got 6-axis colour adjustments, white balance, and gamma controls. 

IO wise you get one HDMI 2.0 port – meaning less than ideal console support – one DisplayPort 1.4 port, and one USB C port for DisplayPort ALT mode. It’s worth noting here too that the USB C port can only provide 7.5W of power, so this won’t be powering your laptop any time soon. It also doesn’t offer a USB hub, so this can’t have your peripherals connected and have a KVM feature to swap between input devices. Physically this is pretty in keeping with Asus’ ROG styling. Especially from the back it’s unmistakably an ROG product, although there aren’t any RGB LEDs in sight. You will find the menu controls here – a joystick style switch for navigation, and three hotkeys to quick-access menus, and the power button at the bottom. One unique feature is the slot in the base, designed to let you stand your phone up in there. That’s pretty nice, although when adjusting the monitor be careful you don’t clobber your phone. Speaking of adjustment, you’ve got plenty of tilt, height, and swivel adjustment, plus you can rotate it to portrait mode if you’d prefer. You’ve also got a VESA mount under the toolless stand mount. 

Right, that’s enough for the tour, let me talk performance, starting with response times. Now, while I did end up testing all TWENTY different overdrive modes, I’ll spare you the pain and suffering and I’ll focus on some of the most interesting findings. The first of which is that, there is actually some amount of difference between the modes. Like there isn’t much between say 3 and 4, but there is a difference. By default the monitor comes on mode 10, so let’s start there. Asus seems to have picked a pretty decent starting point – there is a bit of overshoot across the board, but it isn’t horrendous, and if we look at the initial response time it’s pretty well balanced. You end up with about four milliseconds on average, which puts 87% of the transitions inside the refresh rate window. That’s exactly what you want to see – and it looks like Asus knows what they are doing here. Now they are lying about the “1ms” claimed time, at least with this mode. Let’s look at the maximum, level 20, to see if it’s any better… Ah, no. No it isn’t. See the overshoot here is really, really bad. Unusably bad. Unplayably bad – and none of the results are actually one millisecond, let alone the average! 

Let me show you all the data collated into one graph. The blue line here is the initial response time – just the rising or falling time – and the orange is the perceived response time – including the overshoot time. You can see that beyond a couple of bumps, there is a difference between basically every mode. The floor is around four milliseconds, although you can see the overshoot taking its toll with anything past mode seven. Anything around 7, 8, 9 or 10 is still perfectly fine, but anything past that and you get into worse inverse ghosting than outright ghosting. This is actually a really cool way to see the difference between initial and perceived response times and how overdrive affects your experience. The more overdriven, sure the initial response time is faster, but the actual usable experience gets worse. 

The other thing I tested was on display latency, where I am happy to report the XG27ACS is spot on with an average of around 2.9 milliseconds with very few results spilling into the second frame. That, combined with the decent response times makes for a pretty great gaming experience. Even playing fast paced games like Rainbow Six Siege, it was clear I was the limiting factor in my performance, not the monitor. It’s smooth, responsive, and generally a good time. While I am focusing on FPS games here – I’m confident in saying this is a great choice for pretty much every genre you’d want to play. It’s also pretty bright and vibrant which helps make games look great too. 

Actually testing that reports around 450 nits at peak SDR brightness – that’s actually considerably higher than Asus’ claims, they list 350 nits in SDR or 400 nits peak in HDR, so that’s fantastic. Equally the contrast ratio is a touch better too at more like 1200:1. That’s still pretty naff compared to VA panels or OLEDs, but it’s good for an IPS panel anyway. On metric that, at least in my testing, doesn’t meet Asus’ claims is the colour gamut coverage. Asus lists 97% of the DCI P3 spectrum, but the best I could get was around 90%. That’s still pretty good though so I’m not too worried, and happily the colour accuracy makes up for it with an average DeltaE of just 0.72 – a stunning result. In fact, the worst result is just 1.55, well below the target of 2 we’re generally striving for. That’s excellent. That means content looks rich, vibrant and appealing. If you want to chill and watch some Netflix on this, or even do content creation, this isn’t a bad choice. 

So, to summarise, this is a great gaming monitor. It plays well, it’s smooth, responsive and decently feature-rich. The marketing fluff is a bit much, but legitimately having this many overdrive options is actually pretty cool even if it was torture for me to test them all. At the expected £329 MSRP, that’s an exceptional value for what is otherwise a pretty premium display, and so yeah, this gets a solid recommendation from me.