4K and 5K iMac FAQ: Everything you need to know about Apple's latest computers

OS X El Capitan
OS X El Capitan

If you've been waiting for the entire iMac line to go Retina, it's your lucky day: Apple on Tuesday announced the arrival of the 4K 21.5-inch iMac to its retail and online stores. In addition, the existing 27-inch iMac with Retina 5K display has been improved beyond even last year's spectacular standards. Both have new Intel processors, graphics options, and storage options, along with new Magic Keyboard, Magic Mouse 2, and Magic Trackpad 2 accessories. The best all-in-one desktops in the world have just gotten better, and here's everything you need to know about their new internals and accessories.

What's the resolution of the new 21.5-inch Retina 4K iMac display?

4K, of course! Well, technically even better than 4K: Video 4K is 3840-by-2160 pixels (twice the 1920-by-1080-pixel range of 1080p), or 8.3 million total pixels. Apple's Retina 4K panel, however, is 4096-by-2304—9.4 million pixels in total, and 4.5 times as many as its predecessor. That makes the new 21.5-inch Retina 4K iMac more than twice as sharp as the 21.5-inch iMac of the prior year.

What's more, Apple has also increased the display's color space by 25 percent as well. Beyond sRGB, the iMac has gone to a full P3-based gamut for even truer, more vibrant, and more accurate colors than ever before. That makes photos, videos, and pretty much everything look not only better—but more lifelike as well.

P3-based what now?

DCI-P3 is the color space used by digital movie theaters to achieve the widest gamut possible. Since everything from DSLR to professional video cameras is now capable of shooting beyond sRGB and into DCI-P3, Apple wants to make sure the iMac is capable of displaying it.

To achieve this, the company has upgraded its displays from the standard blue-biased Light-Emitting Diodes (LED) used to illuminate the iMac's display. The new iMac instead uses a more advanced red-green phosphor LED for better balance and wider range. Each panel is also individually color calibrated at Apple's factories using spectroradiometers, and the color management built into OS X keeps things consistent across apps.

Does the 27-inch Retina 5K get the new, higher-gamut panel as well?

It does! The 27-inch's resolution stays the same at 5120x2880, or 14.7 million pixels, but its color space has likewise been updated to a P3-based gamut for the same 25 percent improvement and truer, more vibrant, more accurate colors.

So these are serious displays?

Just a little bit. They'll be great for legibility, which includes everything from reading webpages or iBooks to writing email and working with documents. And, of course, photographers and videographers will love them.

What about processors? Tell me about the processors!

The 21.5-inch Retina 4K iMac ships with Intel's fifth-generation "Broadwell" processors. They start at a 3.1GHz quad-core Intel Core i5, and are configurable up to a 3.3GHz quad-core Intel Core i7. The computer's graphics power is handled by Intel's integrated Iris Pro Graphics 6200 card.

The 27-inch Retina 5K iMac, in contrast, ships with Intel's sixth-generation quad-core "Skylake" processors. They start at a 3.2GHz quad-core Intel Core i5, can step up to a 3.3GHz quad-core Intel Core i5, and are configurable up to 4.0GHz quad-core Intel Core i7.

Graphics options for the Retina 5K iMac include:

  • AMD Radeon R9 M380 with 2GB GDDR5 video memory
  • AMD Radeon R9 M390 with 2GB of video memory
  • AMD Radeon R9 M395 with 2GB of video memory.
  • AMD Radeon R9 M395X with 4GB of GDDR5 video memory.

Wait, rewind: The Retina 5K iMac is leapfrogging Broadwell and going straight to Skylake?

Indeed! It's the same 14-nanometer process as Broadwell, but with a redesigned microarchitecture that brings better performance at greater efficiency.

But no Skylake for the Retina 4K iMac?

Intel hasn't released the Skylake version of the chips used in the 21.5-inch Retina 4K iMac yet. Apple is, however, using the latest versions of the Broadwell chips released just past summer.

How much memory can the new iMacs take?

The 21.5-inch Retina 4K iMac starts at 8GB and is configurable up to 16GB. Unfortunately, you can't change that post-purchase, so make sure you configure your maximum RAM during purchase.

The 27-inch Retina 5K iMac starts at 8GB and is configurable up to 32GB. It retains four user-accessible SO-DIMM slots, so you can upgrade later if you want to.

Both iMacs ship with faster 1867MHz DDR3 memory as well.

Hit me with the storage options!

You can get both the 21-inch Retina 4K iMac and 27-inch Retina 5K iMac with old fashioned hard drives if you really want to: 1 TB 5400-rpm for the Retina 4K, and 1 TB 7200-rpm for the Retina 5K.

More compelling are the Fusion Drives that combine the capacity of hard drives with the performance of flash drives. For the Retina 4K iMac, you can get:

  • 2 TB fusion drive with 128GB of flash

For the Retina 5K iMac, you can get:

  • 2 TB fusion drive with 128GB of flash.
  • 3 TB fusion drive with 128GB of flash.

There's also a new, lower-priced Fusion Drive option for both models:

  • 1 TB hard drive with 24GB of flash.

24GB... is that enough to do anything?

It's enough to store super-important files to make booting, waking from sleep, launching apps, and opening your most-used documents much faster. For anything else, you'll want a beefier Fusion Drive. (Or pure flash storage...)

So the pure flash drive options are still there?

Absolutely! You can get the 21-inch Retina 4K iMac with:

  • 256 GB of flash storage.
  • 512 GB of flash storage.

Or the 27-inch Retina 5K iMac with

  • 256 GB of flash storage.
  • 512 GB of flash storage.
  • 1 TB of flash storage.

This generation of flash storage is 2.5 times faster than the previous generation, as well—hitting 2 GB/s!

What kind of connectivity do the new iMacs have, and how fast is it?

Both the 21-inch Retina 4K iMac and 27-inch Retina 5K iMac have:

  • Two Thunderbolt 2 ports for up to 20 Gbps transfer speeds to external storage
  • SDHC card slot
  • Four USB 3.0 ports
  • Gigabit Ethernet
  • 3.5mm headset jack
  • 802.11ac Wi-Fi clocking in at up to 1.3 Gbps

No Thunderbolt 3 on the Retina 5K iMac?

Nope—not this year.

Do the new iMacs come with the new Magic accessories?

They do! The 21-inch Retina 4K iMac and 27-inch Retina 5K iMac both come with the new Magic Keyboard and Magic Mouse 2, with the new Magic Trackpad 2—with Force Touch!—as an option.

If you'd rather the Magic Trackpad 2 to the Magic Mouse 2, you simply pay the difference.

OS X El Capitan?

It's factory installed!

What about VESA mounts?

You can get versions of both the 21.5-inch Retina 4K iMac or the 27-inch Retina 5K iMac with built in VESA mounts.

I'm intrigued! When and how much?

The 21-inch iMac with Retina 4K display is available from Apple.com, Apple Retail, and select authorized resellers starting at $1499; you can still get older models starting at $1099 and $1299.

The 27-inch iMac with Retina 5K display is available in three configurations from Apple.com, Apple Retail, and select authorized resellers starting at $1799, $1999, and $2299.

Exciting! You'll have more information on all of this, right?

Lots more! Stay tuned for our hands on impressions coming soon. Got any questions for us in the meantime? Leave us a comment!

Rene Ritchie

Rene Ritchie is one of the most respected Apple analysts in the business, reaching a combined audience of over 40 million readers a month. His YouTube channel, Vector, has over 90 thousand subscribers and 14 million views and his podcasts, including Debug, have been downloaded over 20 million times. He also regularly co-hosts MacBreak Weekly for the TWiT network and co-hosted CES Live! and Talk Mobile. Based in Montreal, Rene is a former director of product marketing, web developer, and graphic designer. He's authored several books and appeared on numerous television and radio segments to discuss Apple and the technology industry. When not working, he likes to cook, grapple, and spend time with his friends and family.

  • Nice upgrades but it's really a crime and a shameful money grab to come standard with 5400RPM storage this day in age. I mean heck it was a crime 5 years ago so today it's just blatant greed and disregard for customers. It really truly is just shameful.
  • That's why they offer upgrades. It's easy to demo the advantages of a Fusion Drive in an Apple Store.
  • Apple have also been stupid enough to post a then and now page, (http://www.apple.com/imac/then-and-now/), which shows over the years the advances, and stagnation in the case of hard drives of their iMacs. 5400RPM then, 5400RPM now.
  • It's a 2.5" SATA HDD in the 21.5" & 3.5" in the 27". I agree, Idk why they don't use a 7200 in a desktop.
    If you're concerned about the speed, get the fusion or flash.
    The diff bt 5400v7200 is nothing compared to fusion@5400 or PCI-flash. Sent from the iMore App
  • The difference in speed between a 5400 and a fusion has absolutely nothing to do with anything. If the fusion is using 5400 for its platter then it's still a laughable price for the upgrade, because a lot of OS X is going to be cached on that fusion and if you tend to run a lot of large applications or games then it's still going to be getting a lot of those assets from the 5400RPM platters. It still bad, fusion or not. 5400RPM SSHDs are for Laptops concerned with power management. They really shouldn't have any business in a desktop-class machine - especially at this price point (over a grand). The iMacs should have 7200RPM drives as standard with 7200RPM SSHDs and SSDs as an upgrade. I can see the logic in using them in cheaper Mac Minis, the 2011 MacBook Pro model they still sell, etc.
  • Lotta complaints on here about an HHD that people are never going to use. Faster boot/wake/app launching is all most users really need to percieve their computer as being "faster". Therefore the fusion drive makes a lot of sense for the average user. "...if you tend to run a lot of large applications or games then it's still going to be getting a lot of those assets from the 5400RPM platters" Well not to suggest this statement is accurate, but, many gamers and power users will opt for pure SSD anyway. So this point is moot. "The iMacs should have 7200RPM drives as standard with 7200RPM SSHDs and SSDs as an upgrade." 7200 rmp hasn't ever made much of a difference from 54000 rpm. It doesn't make boot/wake/load app times perceptibly faster. So not sure why you'd lobby for that. Face it, the fusion drive makes a lot of sense for the average user.
  • @nikoli827 I have to agree with you. The FD does make sense for most customers. The new 1TB FD however, is not worthy of being awarded the name fusion drive. I bought and tested the new 27” 5K iMac base model with 1TB FD. It’s horrible… Concerning my daily tasks it is slower than my 2011 MBP with 512GB SSD and 16GB Ram. The new iMac product line disappoints if you are looking for fast office work (FD ! :)) and decent graphics in one machine combined with a big screen.
    IMO one would have to go with the 2TB FD or 512GB SSD (256GB SSD is just too small these days).
    Whatever model you equip with these, you will chuck out around 2,000+ …
    I payed the equivalent of around 2300USD for a new iMac that is beaten by my old 2011MBP. Hence, UPS will send it back tomorrow. Bye, bye iMac.
  • Apple is really pushing the up sale on their hardware now, it's getting ridiculous
  • If you were to equip any new iMac with 512GB of SSD, the biggest model gets you the biggest bang for your buck. $2,938 of these bucks that would be though.. in Germany.
  • Thus, SSD-equipped would be the ONLY consideration for me, over any spindle drive (including Fusion).
  • Will they update the wired keypad to match the new wireless keypad's form factor?
  • Hey itpromike, I Agree with you 100%.....
    I mean come on Apple.... What is wrong with our beloved Apple these Days? .
    I mean come on Now.!!! Pull the trigger on the True Updates.... Please..!!!!
    I love my Apple But, PLEASE..!!!!
  • Any news on whether the new iMacs will support target display mode? That was one of the reasons I skipped the first-gen 5K iMac.
  • Correction:
    3840-by-2160 pixels is considered UHD
    4096-by-2304 pixels is actual 4K
  • Looks like the 27" memory can be upgraded to 64gb http://www.macrumors.com/2015/10/13/27-inch-imac-supports-64-gb-ram/
  • Very disappointed. After several years as a loyal Apple fan, I need to look at alternatives. Apple is too greedy.
  • @let us know how the $400 HP holds up over 6 months time.
  • Did a little research on the graphics card. the 395X 4GB is no faster, and in some cases slower than the 4GB 295x from last years model. No idea why they didn't go nVidia 980m.
  • I've read that the current Nvidia chips can't support a 5k display on a single stream, but the AMD chips can bond two channels together as a single high-bandwidth stream, so AMD was the only choice. Once DisplayPort 1.3 is out this problem should go away. A single DP 1.3 stream can do 5k @ 60Hz.
  • Can anyone tell me the difference between the Radeon M390 and the M395? I can't find anything about it. Thanks.
  • The 5400 HD option is embarrassing, to say the least. In your testing, I am curious to know the speed comparison between the new faster SSD and the Fusion drive. Specifically, does the SSD component also have the same speed as the pure SSD or do they still use the older SSD? Also, just a point of confirmation. Can the iMac drive a 4K TV as a 2nd monitor using AirPlay (or whatever it's called) without choking?
  • Why are people focusing on the default HHD they're never going to use anyway? Why not focus on the fact that you're getting an incredible display AND a powerful computer for a relatively great price? Pay another $100 for the fusion drive and enjoy your fantastic new computer, imo.
  • I did pay that little extra but the smallest FD doesn't do the trick. After testing the base 27" model with 1TB FD, I might go for the mid range model with 256GB SSD with external storage..