21.5-inch iMac with Retina 4K display Experience?

Discussion in 'iMac' started by irock101, Oct 8, 2016.

  1. irock101 macrumors 6502

    irock101

    Joined:
    Jul 26, 2011
    #1
    Hey,

    I am currently using the rMBP in my signature as daily work horse. I have used it with the 4k Dell 27" Display but it's too big for my screen, so I noticed the new 21,5" 4k iMac. How does it compare in terms of speed to the MacBook in my signature? With the standard option it looks like it has half the RAM and no SSD which naturally makes it slower I guess.
    Is the RAM manually upgradable and what is the max?

    Is there any 21" 4k out there that will work with the MacBook in my sig?

    Thanks
     
  2. bbnck, Oct 8, 2016
    Last edited: Oct 8, 2016

    bbnck macrumors 6502

    Joined:
    Mar 19, 2009
    #2
    Only the 27-inch iMacs have user-accessible memory; the memory in the 21-5.inch iMacs are soldered in place, so make sure you customise your iMac to include the amount of memory you'll need for the life of the computer. The 21.5-inch 4K iMac has a very fast processor but from what I can see it's about 20% slower in benchmarks than the 2.5 GHz Intel Core i7 processor in your MacBook Pro.

    SSDs make a substantial difference to overall system performance, especially the kind of SSDs Apple puts in the MacBook Pros, so the slower 5400-rpm hard drive in the iMac 4K will be very noticeable. If you've never used an SSD, then you won't know about the difference and it won't bother you, but as you'll be coming from a fast SSD you'll certainly notice it and may get the impression the iMac is slower. I'll give you an example - my Mid 2013 MacBook Air feels faster than the Late 2014 Mac minis which have faster processors because the SSD in the MacBook Airs (and the MacBook Pros) give the impression that the computer is more powerful than it really is. I noticed when I was running lots of apps simultaneously on the MacBook Air it was able to handle it without a problem, but I didn't realise it was paging to disk during heavy workloads as it was running short on memory (has only 4 GB memory), but the PCie-based SSDs are so quick I barely noticed it.

    My 27-inch iMac has a 7200-rpm hard drive and I certainly notice how much slower it is compared to my Windows PC that has a SATA-based SSD. Actual system performance is faster than my Windows PC which has an AMD Athlon X4-860K, but app launch times and tasks that involve heavy I/O on the iMac are noticeably slower simply because of the 7200-rpm spinning hard drive. It doesn't personally bother me but it does to others and I can understand that.

    You would need to spend at least £1,359 UK / $1,699 US to get a 4K iMac with a 256 GB PCIe-based SSD, so if your MacBook Pro is still serving you fine at the moment but you are considering purchasing an iMac 4K for your desktop set up, then it might be advisable to wait and see if Apple updates their iMacs before the end of the year. A lot of people have their hopes up that the iMacs (and MacBook Pros) will be updated this month, and if they are, it will come as a surprise to everyone if they don't make SSDs a default option in their new iMacs (or at least a Fusion Drive with a minimum 128 GB SSD). From what I've heard, the 1 TB Fusion Drives in the current (Mid 2015) 21.5-inch iMacs only have a 24 GB SSD, which is ridiculous. I don't know if the 1 TB Fusion Drives in the 27-inch iMacs are the same or have a 128 GB SSD.
     
  3. irock101 thread starter macrumors 6502

    irock101

    Joined:
    Jul 26, 2011
  4. bbnck, Oct 8, 2016
    Last edited: Oct 8, 2016

    bbnck macrumors 6502

    Joined:
    Mar 19, 2009
    #4
    I should point out the 27-inch iMacs use faster 7200-rpm hard drives. For whatever reason, Apple decided to put slower 5400-rpm hard drives in the 21.5-inch iMacs. I really don't think its good value to buy a desktop computer with a 5400-rpm hard drive nowadays. Apple should have, at the very least, put a 7200-rpm hard drive across all their iMacs when they were updated last year.
     
  5. irock101 thread starter macrumors 6502

    irock101

    Joined:
    Jul 26, 2011
    #5
    I totally agree. I used to use the 4k Dell in my signature which was the perfect size but since I had to relocate I no longer have space for a 27" screen. I would really like to get one of those 'old' apple cinema displays in 20" or 23" but non retina, non 4k and super dated... just look clean and are cheap to get on eBay.

    Will they work with my rMBP and which adapter do I need? DVI to Thunderbolt? Does that even exist?
     
  6. bbnck, Oct 10, 2016
    Last edited: Oct 10, 2016

    bbnck macrumors 6502

    Joined:
    Mar 19, 2009
    #6
    Don't dismiss a good quality third party external display - there are many great ones on the market. However if you do consider a 4K or 5K display in the future, you just need to pay attention to the native resolution of the display. If it's a 3840 x 2160 display (which isn't quite true 4K but some manufacturers obviously don't care about technicalities), OS X displays the picture on the screen by "pixel doubling," so the effective resolution ends up being 1920 x 1080 (you are still running at the display's native resolution, of course). If you run at another supported effective resolution, OS X can handle it but at a performance hit; since it's not just a simple case of doubling the amount of pixels displayed equally across the display.

    Point being, consider what the effective resolution will be and whether that is OK to you given the screen size. If you run at a resolution that results in a performance hit, it's quite noticeable (and not good either).

    To answer your question about using the Apple Cinema Display, you can use a Mini DisplayPort to DVI adapter to connect a 20-inch or 23-inch Apple Cinema Display with a DVI connector to any Mac with a Thunderbolt or Mini DisplayPort output. For connecting a 30-inch Apple Cinema Display with a DVI connector to a Mac with a Thunderbolt or Mini DisplayPort output, you need to use a Mini DisplayPort to Dual-Link DVI adapter instead. Apple's adapters are overpriced though - you may find cheaper third-party adapters elsewhere from reputable brands that can function to the same standard, but don't vouch me on that - I've never purchased any kind of Mini DisplayPort to DVI adapter as I don't have a display that can only do DVI.

    I am not sure if you are aware but the 4K and 5K iMacs no longer support Target Display Mode (i.e. using the iMac as an external display). If you plan to use an iMac this way, please remember it won't work. I don't know if this will remain the case for the 2016 iMacs (if we get any updates before the end of the year) but I suspect it will be. Target Display Mode was dropped on the Retina 5K iMac when it was first released because of current limitations with the Thunderbolt specification.
     

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