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For a number of years now, 1080p (1920x1080) displays have been the norm for both televisions and computers. And while 4k displays may not replace 1080p as the standard for some time, they have recently been gaining in popularity. These displays have roughly four times the number of pixels as a standard 1080p display which results in a huge improvement in picture quality. But since the technology is still relatively new there are a lot of questions and misunderstandings about this new technology.

Since we have been receiving more and more questions about 4k displays, we decided it was finally time to get our hands on one and perform our own testing. The monitor we will be using for this is the ASUS PQ321Q 31.5 inch UHD Monitor which runs at 3840x2160 with either a 30Hz or 60Hz refresh rate depending on how it is connected to the computer. This monitor offers a range of connectivity options including DisplayPort in both SST and MST mode, HDMI, and dual HDMI. Unlike most 1080p monitors, the type of connectivity you use is very important as it will determine how you setup the display and what refresh rate the display will be able to run.

Currently both HDMI and DisplayPort is limited to 30Hz per 4k display so 60Hz monitors like the ASUS PQ321Q have to be a bit creative to get around this limitation. The way that this monitor and others like achieve 60Hz refresh rates is through the use of either DisplayPort in MST (multi stream transport) mode or by using dual HDMI cables to actually run two sub-4k resolution displays side by side on the one monitor. So you are essentially splitting the monitor in half right down the middle with the left side as one display, and the right side as a second display. By doing this, both displays are actually running at 1920x2160 which can operate at 60Hz with current DisplayPort and HDMI specifications.


http://www.pugetsystems.com/labs/articles/4K-Monitor-Requirements-and-Usage-492/

Interesting bit:
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However, one major discovery we made is that if you have an AMD video card and change the DPI settings, the driver automatically increases the zoom level for internet browsers like IE, Chrome, and Firefox. In our case, when we set the DPI to 146% (140 pixels per inch), IE was automatically set to 145% zoom and Chrome was automatically set to 150% zoom. So very likely the reports of clearer text with AMD cards is simply the result of internet browsers automatically having the zoom level increased which makes text and images on webpages much larger and easier to read.

Other Considerations
4k displays are still relatively new, and as such there are a number of small and not so small bugs. Many of these issues we have already covered such as the dual HDMI issues and the problems we had running at 60Hz with the Intel HD 4600 graphics. In addition to those issues, we had a few others that came up in our testing that did not quite fit in any section.

1. When using DisplayPort in MST mode, NVIDIA cards fail to POST about 50% of the time. When this happens, you have to hit the reboot button on the computer (power off then back on does not work) in order to POST successfully. PC Perspective also had this issue and reported it as an issue with the STMicro firmware on ASUS motherboards. This should be fixed in a firmware update in the near future.

2. NVIDIA and Intel displays in MST mode cannot see the BIOS or POST screens on our ASUS Sabertooth Z87 motherboard. DisplayPort in SST mode and single HDMI, however, work fine. This issue does not happen with AMD video cards.

3. Also related to DisplayPort in MST mode, before the NVIDIA driver is installed you only get a black screen when the OS boots. You have to switch to SST mode, install the NVIDIA driver, then switch back to MST mode.

4. Finally, we initially had some problems when testing HDMI that ended up being due to the cable not being HDMI 1.4a compliant. So unlike SATA cables, make sure your cables are compliant with the latest specification

So much for Nvidia drivers being better ? Their 4k mode is in beta. (AMD Driver 13.4 , NVIDIA DisplayPort Driver Beta 326.41 , NVIDIA HDMI Driver 320.49)

Also web browsing is intense stuff?
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The only potential issue we found was during the 4k web browsing tests where our logging showed the video cards using as much as 1260MB of video memory. To put this into perspective, this is roughly 3 times as much video memory that would have been used if we performed the same tasks on a 1080p monitor.

Since the AMD Radeon HD 7750 only has 1024MB of onboard RAM, this is a potential problem as it is not able to store as much data in it's RAM as it ideally would like to. This didn't result in any noticeable performance difference, but if you want to be sure you are having the best possible experience we would recommend using a video card that has at least 1.5GB of video memory for each 4k display you will be using for these types of tasks.

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Finally, if you are not gaming plan on needing at least 1.5GB of video memory for each 4k display you will be running unless your system is solely used for light tasks such as showing pictures or playing movies. In that case, 1GB of video memory per display should be more than sufficient. If you are gaming, the amount of video memory you need per display is going to depend heavily on the game but will almost certainly be at least 2GB. To be safe we recommend having at least 4GB of video memory per display, but if you play games like Skyrim with lots of mods you may find that you need as much as 6GB of video memory.

Edited by AlphaC - 8/11/13 at 8:31pm
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