Wait for DisplayPort 1.3 for this. It currently uses multi-stream transport to feed the display as if it's two half screens daisy chained together. Sometimes it works, other times it's a trainwreck. At least know what you're getting in to.
Actually, it's not intrinsic to DisplayPort 1.2 that 4k displays must be driven with MST, it's just that for a long time the electronics to decode the full signal were not available, hence the hack.
Starting with the Samsung U28D590D[1], many 4k displays use single stream transport on DP 1.2.
Also, for 5k, you actually have to wait for DisplayPort 1.3 (if you want 60hz), because there's not enough bandwidth, multi stream transport or not. There's a neat bandwidth calculator at [2].
4k is 11.94 GBit/s without overhead, 5k is 21.23 GBit/s. DisplayPort 1.2 and 1.3 are 17.28 Gbit/s and 25.92 Gbit/s respectively.
This unfortunately means no 120hz 5k displays on even DP 1.3 without compression (which is supported).
Oh, good to know. I'd assumed the MST screens were because they had to use it, but I guess I just jumped on the 4K train a few months before I should have...
Correct. Thunderbolt 2 includes support for DP 1.2[1]. And in any case, only has 20 Gbit/s of bandwidth in total, which isn't enough for 5k even without taking overhead into account.
Which makes this announcement quite strange. If this iMac doesn't support Thunderbolt 3 (or whatever standard Apple is planning), it'll never be usable as an external monitor.
IMO, it would have been more Apple-y to launch this and refreshed Mac Pros simultaneously with TB 3, allowing Mac Pros to drive two (or more) 5k displays while the rest of the PC world is still tripping over 4k. But I guess this segment isn't a priority for them any more.
The bandwidth would certainly be there, and there's precedent with monitors requiring dual HDMI to get to 60hz, but I'm not aware of the same thing being done with DisplayPort.
With DisplayPort 1.3 now released, I'd be pretty surprised if manufacturers messed around with dual DP 1.2 inputs for displays like Dell's upcoming 5k. Such things are tolerated when there is no alternative, but when it's just a matter of requiring a new video card for a tenth the price of the high end display, that's the only sensible option. This is extreme early adopter tech after all. 5k is yesterday's 4k.
And needless to say, if I'm speculating it's too messy for Dell, Apple won't touch it with a ten foot pole :)
Still, stranger things have happened. If the demand turns out to be there, the products will follow - it's certainly technically possible.
The 30" Cinema Display had 2 DVI connectors, which was nasty but necessary. So maybe Apple wouldn't be too disgusted by the thought of dual TB.
But if DP 1.3 is around the corner, and dual TB would be an ugly hack that is mutually exclusive with the new standard, I could see them steering clear from that.
In principle, Apple could do something similar again, with an adaptor for two Thunderbolt 2 connectors (from separate buses!) In practice, they'll probably just wait for Displayport 1.3, tho.
Patently false claim. The DVI standard always included dual-link, even before Apple added USB and power connections, changed the connector, and passed it off as a unique invention of theirs.
You don't have to use MST, just that most 4k panels manufactured intentionally mimic two panels so they can output two hdmi 1.4 displays to composite into the whole screen.
I imagine any HDMI 2.0 4k screens to not use it, and even if they are still on DP 1.2, they would start showing a single display.
Sadly, in practice there appear to be many things wrong with DisplayPort. I’m writing this on a machine using a workstation-class graphics card to drive two high-end Dell monitors over DisplayPort. In some respects — starting with basics like what happens when you turn things on and off — it is the least satisfactory video set-up I’ve used in many years, despite being more expensive than the last several put together.
In my experience, for a 2560x1600 samsung monitor, DisplayPort works well. Admittedly, the cable seems to stop working after about 6 months, since I plug and unplug from my laptop twice every day, but a cable replacement works.
In my experience DP doesn't work reliably @ 4k, at least on AMD & Intel GPUs. If you do a bit of Googleing you'll see that there are many problems with DP at super high resolutions. I personally went through 5 different brands of DP cables, a DP MST HUB and all sorts of other remedies and fixes and nothing works reliably. I have 3 ASUS PB278Q and the only input that works reliably is DVI.
