Review Index:

ASUS PQ321Q 31.5-in 4K 60 Hz Tiled Monitor Review

Author: Ryan Shrout
Subject: Displays
Manufacturer: ASUS

DisplayPort 1.2 MST and STMicro Athena Controller

Ah, DisplayPort MST - this mythical technology that has been buzzing in my head since AMD first started talking about multi-display gaming many moons ago.  It is no coincidence that the first thing that shows up when you Google "DisplayPort MST" is a post about Eyefinity and MST capable devices and that I got so excited when I saw a MST hub at CES this past January.  DisplayPort 1.2, apporoved in December of 2009, officially added support for higher bandwidth connectivity and multiple streams for daisy chaining.  Since then it has been a wait for devices to actually utilize it. 

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The platform used on the ASUS PQ321Q is a unique implementation of exactly this.

The ASUS PQ321Q (and the Sharp PN-K321) are both powered by STMicroelectronics Athena controller billed as "a series of innovative System-on-Chip (SoC) controllers designed for multifunctional monitors with a maximum resolution of up to 2560 x 1600 (STDP93x0), 1920 x 1200 (STDP73x0), and 120 Hz FHD (STDP9210)."  Even though it says we are dealing with a max resolution of 2560x1600, there is a lot of headroom on these controllers and when paired up in a multi-head evironment we are able to run parallel 1920x2160 @ 60 Hz screens on a single LCD.

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STMicro "Athena" SoC used in the ASUS PQ321Q

These ICs from STMicro combine DP 1.2 transmitters and receivers in addition to HDMI 1.4 receivers and can support 3D video sources as well.  They can capture up to 4096x2160 resolution video and can scale that down to just about any resolution or it can be passed through to an LVDS connection unchanged.  In the configuration on the monitors in question though they are configured to drive a multi-stream display.

Though I didn't take the PQ321Q apart, I have seen a development board from STMicro and the logic and processing on the system is not insubstantial, with a couple of downscalar boards and quad LVDS connections to the panel itself.  Each display head is responsible for half the screen - up to 1920x2160 at 60 Hz.

Because of the odd configuration, I have seen some comments from readers calling what ASUS, Sharp and STMicro are doing a "hack" to get 4K working at 60 Hz refresh rates.  While you could label it that way I consider it an innovative use of current technologies - by utilizing the multi-stream technology in a single panel we are able to basically push twice the amount of pixels per second than you would otherwise get in a monitor like this.  And the truth is that while DisplayPort 1.2 has the bandwidth to support 4K resolutions at 60 Hz with a single stream, the necessary controllers for that option are not yet available.  Because timing controllers needed for that much bandwidth aren't going to ship at all until early to mid 2014 (likely in small quantities) you can expect the tiled display option to be around for some time to come and remain the budget 60 Hz 4K option as well. 

This doesn't come without some complications of setup as we'll see on the next page of our story here, but I really think that pushing the envelope like this to release higher density panels at consumer cost levels is what the PC industry needs to innovate.

July 19, 2013 | 02:28 PM - Posted by Shambles (not verified)

Whenever I see an external power brick I automatically assume they were cutting as many corners as possible when designing the product. Not that I was going to drop all that money on a monitor anyways, but if I was going to I sure wouldn't be doing it on one that I can't use with a normal power plug.

July 19, 2013 | 04:23 PM - Posted by willmore (not verified)

I'll take an external power brick for any device that I want to live a long time. By separating the power supply and the device, you separate most of the MTBF of the devices. I've had power supplies fail in monitors and they're very hard to fix. Need a generic 19V power brick? That's COTS.

July 19, 2013 | 10:47 PM - Posted by Anonymous (not verified)

Agreed. After years of servicing equipment, I'll gladly take generic external power bricks over internal custom power setups. I even like that they're doing it with a lot of the budget PCs now.

July 19, 2013 | 10:48 PM - Posted by MoFoQ (not verified)

while it is true that most failures of LCD monitors are caused by failing internal power supplies, it is not true that they are difficult to fix.
Some can be a challenge to open, yes but once open, they tend to be easy to repair.
Typically they fall under two categories: blown capacitor(s) or arcing/cold solder on the input power lead. The last two monitors I've repaired, the input power lead had a cold solder which lead to it cracking...then arcing (tiny amounts) plus with the stress of the power cord being plugged in and out, the gap got big enough to do some serious arcing; enough to partial burn that part of the trace.
Fix was easy: clean, resolder or bypass.
For blown capacitors, the hardest part is ordering the right high-quality capacitors.

With that said, using an external power brick has a few additional advantages such as heat.

July 20, 2013 | 12:15 AM - Posted by Inflex (not verified)

$20 replacement power pack, versus (at least) 30 minutes of repair work and replacing $3 worth of caps. Economically in terms of service jobs the $20 replacement pack wins out.

Of course, if you're doing it yourself as a home job or for some fun, no worries, replacing caps is a walk in the park. That said, sometimes it's more complex than that and you just end up wasting time. Up here we get a lot of geckos in power supply units, a lot of the time the whole board is a write off.

November 11, 2013 | 06:33 PM - Posted by Rob (not verified)

> Whenever I see an external power brick I
> automatically assume they were cutting as many
> corners as possible when designing the product.

You do not explain WHY you assume that, nor do you explain why the Manufacturer MUST HAVE been wrong to have designed their Product that way; do you do a LOT of design, or a lot of ...

I would not want to assume about your decision process nor make too many assumptions about the design of something I was not involved in.

In addition to simplified replacement there is the consideration of weight distribution, thinness, ability to switch Power Supply Manufacturers easily (without affecting the portion of the Product where 'the Money' is), heat, interference, Electrical Standards in different Countries, etc. .

Repair may not be as cost effective whether the Power Supply were internal or external, UNLESS they could assume (like Computers) that the End User would most likely be able to do the repair / replacement themselves; which in the case of Monitors / TVs is NOT going to happen).

In addition, in the event that you are partially correct somehow, this is "one corner" that was cut; why assume they cut as many corners as possible. If you do not like a single decision they made in the design then you assume the rest is a bunch of junk.

May I suggest, without assuming for others, that is something not well understood, or perhaps well explained.

Rob -

April 15, 2017 | 08:04 PM - Posted by Valendi

A power supply generates quite high EMFs or magnetic and magnetic fields. Certainly you don't want them near your face or any part of your body.
The example is the NEC MultiSyc LCD2170NX, which has the power supply behind the screen (and high voltage too, 230VAC equals 325 volts peak. Not very safe but the most important part the mentioned earlier.

July 19, 2013 | 05:57 PM - Posted by brucek2

Thanks Ryan for an informative article that answered all of my most burning questions. As you mentioned there are more details to explore, but your top line findings are already enough for me to know that its probably best to hang back a bit before pressing that buy button (it sounds like they are going to get there though and that's great.)

July 20, 2013 | 09:57 AM - Posted by NLPsajeeth

Ryan that was an awesome article. Since I doubt anyone is going to risk opening a $3500 monitor I didn't think I'd ever find out what TCONs are driving the panel but you went above and beyond and got the info! Great Job!

It is still too bad NVIDIA refuses to support 2x1 and 2x2 surround for all monitors not just these tiled 4K displays. I was hoping that if a ton of these tiled displays hit the market, NVIDIA would be forced to add proper Surround support instead of white-listing monitors. But if what you said about the new standards comes to pass, they will probably be able to support these tiled monitors while still preventing generic 2x1 and 2x2 Surround. Too Bad.

DisplayPort 1.3 is under development. With all the delays I wonder what will get finalized first DP 1.3 or HDMI 2.0. I hope the DP 1.3 is as ahead of its time as DP 1.2 was in 2009. Here's hoping for 8K @ 120 Hz over a single cable. That would be awesome.

July 19, 2013 | 09:09 PM - Posted by Anonymous (not verified)

define "tiled" ?

July 20, 2013 | 11:30 AM - Posted by Ryan Shrout

Tiled means there are multiple heads in side the display.

July 19, 2013 | 09:27 PM - Posted by Anonymous (not verified)

Would be interesting to know if there's any additional early adopter problems by using two/three of these monitors. I suspect that drivers are full of bugs for this corner case. One obvious problem with Windows7 might be that the taskbar is stretched over both monitors because of Eyefinity/Surround must be enabled.

July 20, 2013 | 11:31 AM - Posted by Ryan Shrout

I would suspect that any issues that plague Eyefinity or Surround would be in play here, yes.

July 19, 2013 | 09:58 PM - Posted by EndTimeKeeper

Great Article, it makes me want one even more lol. I have a silly question how would this monitor work if you where to hook up something like a sony playstation 3 to it? The reason I'm curious is that I run both my PS3 and my computer on my monitor and was wondering if I could still run a setup like that if I was ever to get a monitor like this one?

July 20, 2013 | 11:28 AM - Posted by TMoney58 (not verified)

It works exactly like you'd expect. I have the PQ321 and I have my PS3 plugged into one of the HDMI ports while my PC uses the Display Port.

July 19, 2013 | 10:55 PM - Posted by Anonymous (not verified)

It's VESA DisplayPort 1.2 and VESA DisplayID 1.3 specs that enable this monitor. DisplayID is the next generation of the ancient VESA EDID standard. DisplayPort. 1.2 added MST support.

July 20, 2013 | 10:06 AM - Posted by NLPsajeeth

It was odd that Ryan was referring to DisplayPort 1.2 by name in the article and then started talk about "VESA 1.3". It seems that DisplayID v1.3 was indeed ratified by VESA in April or May. It certainly make sense for a monitor to advertise itself as tiled via DisplayID/EDID.

Since the spec was just finalized I'm guessing it will probably be a while before it makes its way into display controllers.

July 19, 2013 | 11:07 PM - Posted by Anonymous (not verified)

Thanks for the article. I'm one of those interested in knowing how the monitor scaled/pixel doubled from 1920 and that tiny bit of info about it being unsupported with MST saved me $3500. I guess I'll be waiting for the 4k/60hz TCON panels to come out.

July 19, 2013 | 11:26 PM - Posted by Sean Harlow (not verified)

"If you had the ability to run each side at 1920x2160 (taking up the entire left and right side of the screens) there might be more utility but ASUS told me that wasn't yet on the roadmap."

What's different about this than how the dual HDMI mode operates? Why couldn't you just put the monitor in that mode, but attach different devices to each port?

July 20, 2013 | 11:32 AM - Posted by Ryan Shrout

Perhaps nothing, but Dual HDMI assumes the two inputs are the same input.

July 20, 2013 | 02:13 AM - Posted by Branthog

I know it's lame, but even though this has such a high resolution, the 16:9 aspect really puts me off. Do we really enjoy swiveling our head left and right all the time at our desks?

July 22, 2013 | 12:05 AM - Posted by Anonymous (not verified)

Yes we do, that's a lot more enjoyable than looking up and down.

May 12, 2015 | 07:51 AM - Posted by bobber frames (not verified)

Good post. I will be experiencing some of these
issues as well..

July 20, 2013 | 02:25 AM - Posted by Anonymous (not verified)

I'd be interested to see this display tested on different Apple hardware. I have a hard time finding information what for instance newer macbook (air/pro) handles. Also, no tests were done with Intel hardware, does that mean it's a no-go with Intel 4000 chipset?

July 20, 2013 | 10:16 AM - Posted by NLPsajeeth

Apple maintains strict control over video drivers on OS X so it is possible they may not support using 4K@60p with this monitor.

PCper did tests with Intel hardware in their unbox/preview video. Intel's Collage feature supports 2x1, 3x1, 4x1 and 4x4 monitor configurations and is available on Ivy Bridge (like the Intel HD 4000) and Haswell integrated GPUs.

July 20, 2013 | 02:28 AM - Posted by Anonymous (not verified)

Great article as always Ryan! There are a couple of things I would like to see going forward. First, 8x AA is way beyond overkill at 4k res to be sure. Let's look into exactly how much AA is need at 3840x2160. Show us more screenshots and in-game assets like that Skyrim tree at different modes and levels of AA. And let's also look into how much of a performance hit they will have. Though I imagine AA will cost about the same amount of performance it could possibly be different than what we are used to seeing with resolutions that are more commonly used today. Keep up the good work for us all!

July 20, 2013 | 05:18 AM - Posted by Hung Low (not verified)

correct me if I'm wrong. I have a rMBP, which has a GTX 650M and thunderbolt port. If I buy this monitor, I would be able to plug a display port cable into the TB port and drive the monitor?

July 20, 2013 | 10:10 AM - Posted by NLPsajeeth

Yes but 4K@60p may not work in OS X. NVIDIA had to put a special driver hack in the Windows driver to make the monitor work due to their artificially crippled drivers. Apple maintains tight control over the Mac OS X NVIDIA driver which is even more crippled than the Windows driver. It may not support tiled displays.

July 20, 2013 | 11:30 AM - Posted by Ryan Shrout

We hooked the MBA that Ken has up to this monitor through DisplayPort and could NOT go higher than 1920x1080.

August 10, 2013 | 02:06 AM - Posted by Luke Abell (not verified)

Ryan- have you tried hooking it up to a Macbook Pro Retina? Or the new 2012 iMac?

July 22, 2013 | 03:08 PM - Posted by mLocke

Will 120hz ever become mainstream? *sigh*

July 23, 2013 | 10:08 AM - Posted by AndyT (not verified)

"The first problem was an occasional ability to fail a cold boot"
"Another potential problem was the lack of ability to see the POST screen and BIOS during boot"
This is basically not consumer ready on nVidia hardware right now. Or is it just me that wouldn't want to put up with that level of crap from a $4500 GPU + display combination?

July 26, 2013 | 07:14 AM - Posted by Anonymous (not verified)

Is there any unusual behavior when doing MST with either the monitor put into portrait mode directly via OSD, or through windows control panels? How the drivers react to portrait mode can be a problem. Additionally, how are the viewing angles when in portrait mode, as many displays have polarization filters that look fine in landscape, but in portrait orientation screw up the brightness as perceived by the eye. Finally, it appears the control buttons are sufficiently recessed so you can align multiple monitor bezels to touch each other without pressing them, but can you confirm that?

July 26, 2013 | 11:40 AM - Posted by Anonymous (not verified)

The need for MST or tiling in general makes me think now isn't really the time for 4k on the desktop, unless you're working in an industry that can very obviously make use of the added resolution.

I'd rather wait for the next revision of DP or HDMI so the monitor can be driven at native res, at 60 or even 120Hz with just one proper connection. That pretty much means waiting for the next generation of GPUs and monitors.

July 31, 2013 | 09:24 AM - Posted by Anonymous (not verified)

The new driver version 326.41 adds support for tiled 4k monitors.

August 6, 2013 | 12:45 PM - Posted by Anonymous (not verified)

what about three of these in eyefinity :) ?

August 22, 2013 | 07:33 AM - Posted by Anonymous (not verified)

Has anyone tried hooking up 3 PQ321Q in one machine?
Do u think it is doable?

October 6, 2013 | 12:28 AM - Posted by gohkg (not verified)

Hi, wonder if anyone can help. Bought a Asus PQ321, the display is great but somehow i cannot set it to 60Hz using MST whether be it using a GTX690 or AMD 6990 graphics card. Always one half of the panel is blank after setting MST for either cards and both cards cannot detect the blank half and for AMD i cannot even set up Eyeinfinity group...thanks.

December 24, 2013 | 05:01 AM - Posted by ZaraPerkins (not verified)

What do you think about the Sharp, its cheaper and has the same 4k technology, pretty interested to see if there is much of a difference that matters in price point here. Thanks for any help or advice.

December 24, 2013 | 05:03 AM - Posted by ZaraPerkins (not verified)

What about the Sharp PN?, similar in 4k technology but the price points much less for the Sharp, what would be your bigger decision factor between the two?

February 28, 2014 | 02:29 AM - Posted by kiwi (not verified)

This screen runs 4k @60hz, on the new Mac Pro. I have a new Mac Pro (since two days ago), but I don't have this screen yet. I'm about to order it.
This screen, and the Sharp PN-K321, are the two screens whitelisted on apple support page, as running 4k @60hz.
No doubt that list will grow as drivers and stuff get sorted.

Note that SwitchResX gives you a gazillion times more control over the available screen resolutions and refresh rates on Macs. You can even do your own custom ones. So anyone who can't get particular resolution or refresh rate that they want, give SwitchResX a try.

And to mLocke who wants 120hz to become mainstream, well I'm doing my bit. On my MacBook Pro 15"" Retina, mid 2012, and using SwitchResx, I was able to get 1920 x 1080 @120hz (on an Asus VG248QE). 120hz is stunning. (It needed the Apple mini display port to dual link DVI adaptor)

November 25, 2014 | 09:06 PM - Posted by Anonymous (not verified)

How do i do this with intel integrated graphic???

At the moment i'm running the 4k at 3000x1600 and 45hrtz.
When i try to combine it just goes to 30htz