My 24in Apple Cinema Display is well past its sell-by date. It soldiers on, with no Thunderbolt port and old-fashioned USB 2 connectors, but I have long wanted to upgrade. The arrival of the 5K iMac looks like a good starting point for the development of a really scintillating 5K display to go with the new Mac Pro and with the range of Apple laptops. But, for very good technical reasons, such an external display is a long way away. This is how Marco Arment explains the Cinema Display dilemma in his excellent review of the 5K iMac:
If I had to guess, you’ll have a long wait, and they won’t work with any Mac sold to date. Panel yields may be tight for a while, and external displays are a low priority for Apple. The original 27” iMac’s groundbreaking LCD panel wasn’t available in an external display from Apple for almost a year after its release. But that’s not the biggest problem.
Pushing this many pixels requires more bandwidth than DisplayPort 1.2 offers, which is what Thunderbolt 2 ports use for outputting video signals. (I wrote about this a few times.) Doing it right will require waiting until DisplayPort 1.3 in Thunderbolt 3 on Broadwell’s successor, Skylake, which isn’t supposed to come out for at least another year — and Intel is even worse at estimating ship dates than I am, so it’s likely to be longer.
It may be possible to use two DisplayPort 1.2 or Thunderbolt 2 cables to power a 5K display, but only if the GPU could treat each port as its own full-bandwidth DisplayPort 1.2 channel, the sum of which represented one logical display, and had the panel combine and properly sync the two at the other end.1 I don’t think any of the current Macs can do this, including the Mac Pro — MST to run 4K panels at 60 Hz only seems to be supported within individual ports, not spanned across two.
I’d estimate — granted, I’m wrong a lot — that Apple won’t ship a standalone 5K display until at least 2016, and it won’t work with any of today’s Macs, including the 2013 Mac Pro.
This is a great pity and I am certainly not alone in continuing to coddle the old Cinema Display in the hope of a superior replacement. In many respects, buying a separate high-definition display makes more sense than getting the new iMac because the display can easily serve several generations of computer.
My display is now over six years old and, in view of the original cost, has proved a bargain. It has been hooked up to at least four laptops, including a couple of Airs, a 13in MBP and the current 15in retina. I could have gone through three or even four iMacs in that time, all with perfectly good displays, rendered obsolete before their time by the internal processing technology. Unfortunately, if I do want a large 5K screen it now looks as though the iMac is the only choice. My 15in MacBook Pro with retina screen is coming up for replacement in 2015 and I will probably be forced to swap it for an iMac as I pension off the old Cinema Display.