Why would you want your 5K iMac as an external display

Discussion in 'iMac' started by roadkill401, May 2, 2015.

  1. roadkill401 macrumors 6502


    Jan 11, 2015
    I have seen it here time and time again, people saying they are going to wait for the next generation of iMac as the current version will not let you use the 5K screen at an external display.

    I am curious as to why you would want to do that? Would you not think that by the time the next itteration of 5K iMac comes around that they cost of a stand along 5K screen will have dropped well below the cost of what the next 5K iMac costs??

    The only reason I can think of for wanting to use the display externally is that when the iMac becomes functionally obsolete in there are much faster processors out there and this Mac is just too slow to be useful, then you can save the screen to use as a second display.

    But on the flip side to that. I would not say that moors law has held up in the top end i7-2600K cpu that I bought over 4 years ago is 15-20% slower than my new i7-4790K chip inside my new 5K iMac. If CPU speed follows the same trajectory, in 5 years when they consider this iMac obsolete, the speed of the newest CPU won't be much better than what I have now. So as long as this computer still works, it will be just as functional.

    What will likely change is we will be using 8k or who knows what sort screen that will make the point of wanting to slave this screen as moot.

    Am I missing something here?
  2. theluggage macrumors 68040

    Jul 29, 2011
    Usually, because you have more than one computer that you want to connect to a large display.

    One scenario: you have a home iMac and a work laptop. Sometimes, you work at home, and want to plug your laptop into a large screen.

    If you're just working with straightforward documents then sure, you can sync your machines somehow or use the cloud - but life isn't always that simple. If you're editing a video project, building a data-driven website, using multiple virtual machines for testing etc. than "syncing" might mean half-an-hour of faffing around before you can get to work, and again when you are finished. Or, you may have software on your laptop that isn't licensed for your home machine. Or, you might just want to keep a clear line between work and home.

    Scenario 2: you buy a shiny new iMac, but keep your old mini as a backup machine and media server. Mostly it doesn't need a display, but sometimes you need to work on it. Or maybe there some old software you need to use occasionally that won't run on the latest OS X.

    Scenario 3: you buy a shiny new iMac, but like to play the latest 3D shooters, so you get a games console as well.


    Most decent 3rd party displays have 2-3 separate inputs that you can switch between. Apple displays - and the riMacs - are a bit impoverished in that respect.
  3. redheeler macrumors 604


    Oct 17, 2014
    I was using my 2010 iMac in Target Display Mode as a display for my Mac mini. After I got my 5K, my mini became headless with Screen Sharing over Thunderbolt Bridge, which has worked fine for me despite some lag and a very low refresh rate at 4K. It fits neatly in a window and shares the iMac's keyboard/mouse.

    I agree that while Target Display Mode is a convenience, it shouldn't be the sole deciding factor for anyone looking to get an iMac. For anyone looking for a standalone 5K display for a Mac Pro, Dell makes a nice one.


    Screen Sharing over Thunderbolt Bridge works just fine for a Mac mini used this way. Snow Leopard Server can be virtualized.

    Target Display Mode on all iMacs since the mid 2011 requires Thunderbolt. Most consoles only have Mini DisplayPort output. So this wouldn't work even if Target Display Mode is supported on the 5K.
  4. Liffey macrumors regular

    Feb 2, 2010
    Someday my 5k iMac will be out of date and I'll buy a new one, but I may want to keep the 5k monitor as a second display.
  5. theluggage macrumors 68040

    Jul 29, 2011
    Yes - and that's a disadvantage of iMacs, too. A comparable stand-alone display will typically offer at least two switchable inputs of various types.

    The problem is that the new Mac Pro is too much of a specialist machine (for people who need to do 72 hour renders that can make use of twin GPUs and need the stability of the Xeon and ECC RAM) with a price to match.

    There's a big hole in the Apple line-up where a headless quad-i7 desktop with a decent non-workstation GPU should be. The hole is there for good reasons (from Apple's point-of-view) but its still a nuisance.

    Maybe I should Hackintosh the ridiculously-overpowered HTPC box I built last year...
  6. MacVidCards Suspended

    Nov 17, 2008
    Hollywood, CA
    The answer to this question is at Barefeats.com.

    He just compared 5K imac to nMP and cMP running 5K.

    The Retina imac did win one test IIRC. But for most part it was a slaughter.
  7. roadkill401 thread starter macrumors 6502


    Jan 11, 2015
    But as I pointed out in my OP, Moors law use to mean that with the 1/2 of the cpu die size, the speed of the processor doubled as a consequence. Then when they hit the wall with CPU speeds, they started adding number of cores. Then they figured out how to Hyperthread.

    But if you compare the mainstream i7 CPU from 4 years ago (Sandy Bridge i7-2600k) to the mainstream i7 CPU from today (Haswell i7-4790k) the actual computing power using any of the modern testing software puts it at 15-20% improvement.

    The Sandy bridge was 32nm die, where Haswell is 22nm and 2 generations of CPU beyond, but in reality didn't really make that much of a difference. Who knows is Broadwell will make a huge difference? I don't, but if you look to historical performance trending, you will see that the improvements have been flattening out over the years and generations of CPUs. It would not surprise me if the top end Broadwell is only nominally better in speed that the current Haswell chip.

    It might bring other goodies like better power efficiency or run's far cooler so Apple can make an even thinner iMac.. but that has no effect on performance. We might be reaching the point of diminishing return that until we make some quantum leap the speed of CPU's might have hit the preverbal wall.
  8. Liffey macrumors regular

    Feb 2, 2010
    We're not even close to the end of the line. High end PCs absolutely trash current 5k Macs for example.

    Now, whether that's actually useful to most people might be in question, but nevertheless technology will continue to improve.

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