Can the 5k iMac support another 4k display without lag?

Discussion in 'iMac' started by cmm, Jan 24, 2015.

  1. cmm macrumors 6502a

    Apr 30, 2006
    I’m in a bit of a pickle and need some advice. I thank you in advance for reading this lengthy post and adding your input!

    I had the current model rMBP 15 with discrete graphics. It was great, but I wanted something more portable, so I went to the current model rMBP. Both laptops had 8GB of ram and a 512 SSD. I have a 27” Thunderbolt Apple Cinema Display, however I’d like to sell it and get a good 4k display (60hz Samsung). Maybe I’m glorifying the 15 rMBP because I’m having such problems with my 13 rMBP?

    The 15 rMBP didn’t lag as much (I keep about 15 windows open), I assume due to its GPU. I am getting very annoyed with the lag and beach balls occurs at least twice a day with my current machine. I am constantly swapping more than 1GB. For example, I have 20 tabs open in Safari now (I don’t use Chrome since it’s a memory hog), mail, adium, skype, messages, textual, textedit, 2do, sublime text, rubymine, terminal and preview open. Uptime says I haven’t rebooted for 5 days and Activity Monitor shows I’m using ~600MB of swap.

    I write code all day and use various development tools. I have several VMWare VMs I run, but no more than 2 at a time (these will live on the external Thunderbolt enclosure). I never game. Occasional 1080p playback, but most of the time, I play the media off my FreeNAS box to my xbmc HTPC in my living room—more often than 1080p, will I watch clips on youtube (in HTML5 when possible). Any crunching I have to do, I will run on the computers at work.

    I’m trying to decide what to do: Should I purchase a 15 rMBP with Iris Pro graphics or a dedicated GPU? Should I get a 5k iMac and plug in a 4k monitor (I have heard reports that the graphics card in the 5k iMac isn’t as powerful as it should be and I may experience lag issues when running a second monitor). Or, should I buy a Mac Pro (more or less the base model, however, I’ll probably install 32GB of ram), which should easily support 2 4k monitors, and I can always add a third later on. Which graphics card do I need for the Mac Pro? Is base okay for my needs? Do I really need the discrete graphics card for the 15 rMBP, or will Intel Iris Pro be fine to power one more 4k monitor?

    Most important thing is NO MORE LAG. It’s like I’m back in the mechanical disk age, when I wanted to throw the computer out the window several times a day (although, admittedly, it isn’t that bad yet).

    If I go with the rMBP, I will max out the memory to 16gb. If I go with the 5k iMac, should I start with 16gb of ram or go to 32gb, I was hoping to go with a 256GB or 512GB SSD, depending on the price difference, as I already have a 20TB FreeNAS box running raidz2 that holds all my media (bluray movies and music)…I have 2TB free right now. I am planning on purchasing a 2 bay thunderbolt enclosure for 2 512GB SSDs to hold all my documents (as I use owncloud) and my 200GB picture collection. Of course I have another server for backups of everything.

    I do like the idea of having ECC ram, which the Mac Pro has. I like that it can support 3 4k monitors, but that’s a total luxury… I would be happy with just one extra 4k monitor. I never thought I’d go back to a desktop, but the iMac and mac Pro isn’t that hard to carry around on occasion.

    I am considering a few monitors, but this one is a particularly good deal: $600 for a 4k 60hz 28” monitor

    If it matters, I plan on running the extra 4k monitor in “retina” mode, i.e., high DPI, so not the full 3840x2160 resolution, if that matters? I like the crispness of the retina screen and I assume the text isn’t as crisp at 3840x2160…
  2. ra004e macrumors regular

    Jun 8, 2009
    I have base unit riMac 5k and as long as you turn on System Preferences > Accessibility > Increase contrast ( you will loose Yosemite UI transparency ) you will be able to drive additional 4k with almost no lag, I say almost, as once you open enough windows it will eventually start to lag a little even with just the built in display. Your usage seems somewhat similar mine and I would opt for M295X with 4GB for best performance as I've had both, but you still should turn on System Preferences > Accessibility > Increase contrast to minimize lag.

    Full 3840x2160 resolution actually lags less ( my observation ) as there is no scaling performed as with the "retina modes". I've also found that "best for display" retina setting create the least amount of lag of the scaled modes. Hope this helps.
  3. cmm thread starter macrumors 6502a

    Apr 30, 2006
    But I really like the transparency :(

    That stinks. I guess I need to wait for a new revision of the 5k iMac with a better GPU. I guess I will stick with the Mac Pro and run 3 4k displays. Or, maybe I will sell my 13 rMBP and get a 15 rMBP and try my luck with two 4k 60hz monitors at retina/1080p. Do you know if the discrete GPU is any better in the 15 rMBP.

    NB I currently have a 13 rMBP with 8GB of ram (not enough) and a Mac Pro. I was really hoping to change my workflow and get a 5k iMac with one 24" Dell IPS 4k 60hz display for the ultimate workflow. But now it looks like I'll need to get the 15 rMBP with two 24" Dell 4k 60hz displays.

    What do you think? Or do you think the discrete GPU in the 15 rMBP will lag as well? I just don't do anything that needs the computational power of a multicore Xeon, although, I do appreciate ECC RAM...

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