iMac 21.5-inch (2017) preview

iMac 21.5-inch (2017) preview

The 21-inch iMac was last updated in October 2015 and, to be frank, that update was a little disappointing because, despite the fact that this was the first generation of 21-inch iMac to offer a 4K Retina display, the processor in that model was a Broadwell CPU, rather than the Skylake CPU offered by the 27-inch iMac of the same generation.

The good news is that this time round both the 21-inch iMac and the 27-inch iMac have received a processor boost to the newer Intel Kaby Lake range. So no more lagging behind for the 21-inch model.

The other big change this time round is that where in 2015 there was only one 21-inch iMac with a 4K Retina display. This time round there are two models offering 4K displays. These two 4K iMacs also offer discreet graphics processors, rather than the integrated Intel graphics that had been offered on older generations.

As a result, these 4K iMacs, with their quad-core Kaby Lake processors, Radeon Pro graphics cards, and the option to configure RAM to 32GB, are looking more powerful than ever.

We’ll take a more in-depth look at all the aspects of the new models below, starting with display.


When it updated the iMac in 2015, Apple added a 4K Retina display to the 21-inch range. This time round there are two 4K Retina iMacs: a 3GHz quad-core model and a 3.4GHz model.

At launch in 2015 the 3.1GHz 4K 2015 model with a Retina display cost £1,199. This year’s entry-level 4K Retina, with its 3GHz processor, costs slightly more at £1,249. However, we should note that the prices of the previous generation iMac increased in October 2017, so that model was eventually priced at £1,449. So in some ways Apple could sell this as a price drop (and will probably try to).

As for the 4K display Apple’s made some improvements there. All the new iMacs with Retina displays (including the 27-inch models reviewed here) feature new Retina displays with 500nits and 10-bit dithering, which probably sounds like gobbledegook to anyone who doesn’t speak ‘monitor’ but basically means that they are 43 per cent brighter and capable of reproducing even more colours –  one billion colours, according to the company.

Apple says that iMac users will be able to enjoy an “even more vivid and true-to-life viewing experience” from these new screens.

The resolution is the same as before, at 4,096×2,304 pixels for the 21-inch Retina iMacs. This is a P3 display, as per the 2015 models. A P3 display is capable of producing colours outside the sRGB colour gamut.

The non-Retina 2.3GHz model offers a 1920×1080 sRGB display. It is possible that if you didn’t see the Retina display model you would be more than satisfied with the standard display on the entry-level iMac. But at just £200 extra, and with the other benefits the Retina model brings (faster processor, better graphics) we think it’s worth considering the pricier 3GHz Retina model.

It’s interesting to note that the £1,249 Retina display 3GHz iMac has the same price attached to it as the 12-inch MacBook, which offers a 1.2GHz processor, and the 2.3GHz 13-inch MacBook Pro. You won’t get a Retina display for less than £1,249 and the iMac certainly looks like it offers the best value for money.


All the new 21-inch and 27-inch iMacs will feature new Intel Kaby Lake processors. The 21in iMac models will get Kaby Lake processors running at up to 3.6 GHz. The processors are as follows:

21.5in iMac
•    2.3GHz i5 dual-core
•    3.0GHz i5 quad-core
•    3.4GHz i5 quad-core
•    3.6GHz i7 quad-core (BTO)
27in iMac
•    3.4GHz i5 quad-core
•    3.5GHz i5 quad-core
•    3.8GHz i5 quad-core
•    4.2GHz i7 quad-core (BTO)

As you can see, it is not the case that the 27-inch iMac offers a huge jump in comparison to 21-inch models, which is a significant difference to the MacBook Pro where there is quite a leap between the siblings.

Here you can choose a 3.4GHz iMac in either 4K or 5K resolution, for example. One will cost you £1,449 and the other costs £1,749.

Compared to the last generation models, the new Kaby Lake processors will make a big difference. In 2015 the 21-inch iMac was hampered by older Broadwell processors while that year’s 27-inch models had the Skylake processor. ?
Since the 21-inch model are jumping two processor generations so you can expect to see some real gains compared to the older models.

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We are currently testing the new iMacs and will add the results here as soon as we have them. For now, here is the testing for the 2015 Retina 4K model and the 2013 models.


21.5 3.1GHz 4K 2015 model

Geekbench 3 single-core 64 bit

  • 3.1GHz 21.5in 4K iMac : 3,783
  • 3.3GHz 27in 5K iMac (mid 2015) : 3,691
  • 2.9GHz 21.5in iMac (late 2013) : 3,543
  • 2.7GHz 21.5in iMac (late 2013) : 3,175

Geekbench 3 multi-core 64 bit

  • 3.1GHz 21.5in 4K iMac : 12,799
  • 3.3GHz 27in 5K iMac (mid 2015) : 11,769
  • 2.9GHz 21.5in iMac (late 2013) : 10,683
  • 2.7GHz 21.5in iMac (late 2013) : 10,199

The entry-level model is an improvement on the 2015 entry-level iMac. Back then the cheaper model offered a measly 1.6GHz processor. Now the entry-level is a more attractive 2.3GHz.

However, there is a caveat. When that 1.6GHz processor first arrived the entry-level iMac price was just £899. So the price is now £150 more.

However, as we mentioned above, Apple did rase the price of the iMac back in October 2016, so the entry-level 1.6GHz model was £1,049 more recently. Meaning that Apple has effectively removed the old entry-level specced machine from the line up and replaced it with an update to what was the 2.8GHz non Retina 4K model, which cost £1,049 at launch, and later cost £1,249.

What that all boils down to is the fact that you can get a 2.3GHz iMac for the same price as you used to get a 1.6GHz iMac. And this new 2.3GHz model sits somewhere between the older 1.6GHz and 2.8GHz models.

It definitely has more going for it than the old 1.6GHz model which we would have dissuaded anyone from buying.

However, as we said above, for just £200 pounds more you can get a Retina display, but also a 3GHz processor and a discrete graphics card. If you would benefit from these improvements its well worth paying the extra cash.

One last, thing about the iMac processor. The processor is accessible and upgradable, according to iFixit. Yes, Apple has made it possible for users to upgrade their iMac, something that has been impossible in recent years. Doing so will void your warranty, or course, but since updates tend to happen years down the line we doubt this matters to you.


If that wasn’t reason enough to buy the new iMac, then here’s another. It is also possible to upgrade the RAM yourself.

This discovery was also made by iFixIt, who were shocked to find that rather than being soldered onto the motherboard, this time the RAM is located in a RAM hatch hidden behind the logic board. So the RAM can be upgraded.

The fact that these components can be upgraded is a refreshing change, although accessing them will not be easy.

Nevertheless it is great to see Apple making changes that will please typically creative users who want upgradable Macs. It may point to the forthcoming iMac Pro and Mac Pro being user upgradable.

The memory is better too – it’s been upgraded to DDR4 and therefore offers higher clock speeds and lower voltage operations and is faster than the older DDR3 memory.


It’s not just the Retina display you get if you pay £200 more than the entry price. You also get a dedicated graphics card, the Radeon Pro 555 with 2GB video memory, rather than the Intel Iris Plus Graphics 640.

Intel’s graphics (which are integrated on to the CPU) use the computer’s RAM, while dedicated (or discreet graphics cards have their own memory.

An integrated card will be quite sufficient if you are just using your Mac for things like browsing the web, office work, even watching and editing videos. But if you do graphic intensive work – perhaps you are a designer, or maybe you like to play games on your Mac – you will benefit from the Radeon Pro graphics cards offered on all the other machines.

Back in 2015 all the 21-inch iMacs, even the top of the range, 4K iMac, featured Intel Iris Pro Graphics 6200. Now all but the entry level iMac are getting discrete Radeon Pro graphics cards.

The 4K iMac will ship with discrete Radeon Pro 555 and 560 4GB VRAM, which is 3x faster than the previous generation, according to Apple.

The 21.5-inch model delivers up to three times faster performance than previously, and the 27-inch model is up to 50 percent faster, according to Apple.

Even though the entry-level 21-inch iMac gets an Intel’s Iris Plus integrated graphics, that is still 80 percent faster than previous generation.

Apple’s decision to use discrete graphics on the 21-inch Retina Macs in 2017 suggests to us that Apple is reacting to increased interest from graphics professionals and gamers.

One thing is for sure, judging from the WWDC keynote presentation in June, at which Apple said the new iMacs offer a “big jump in graphics performance.” Apple wants to get into the Virtual Reality revolution, and to do so, Macs need to have the right graphics cards.

We are currently testing the new iMac’s graphics prowess, in the meantime, here are the figures for the 2015 model.

3.1GHz 4K 2015

Cinebench R15 CPU

  • 3.1GHz 21.5in 4K iMac : 72 (less is better)
  • 2.9GHz 21.5in iMac (late 2013) 3,543 : 88
  • 2.7GHz 21.5in iMac (late 2013) 3,175 : 100

Cinebench R15 OpenGL

  • 3.1GHz 21.5in 4K iMac : 47
  • 3.3GHz 27in 5K iMac (mid 2015) : 87 (higher is better)
  • 2.9GHz 21.5in iMac (late 2013) : 55
  • 2.7GHz 21.5in iMac (late 2013) : 29.2

Unigine Heaven 1920×1080 OpenGL

  • 3.1GHz 21.5in 4K iMac : 18.5 (higher is better)
  • 2.9GHz 21.5in iMac (late 2013) : 10.6
  • 2.7GHz 21.5in iMac (late 2013) : 7.2

Unigine Heaven 1280×720 OpenGL

  • 3.1GHz 21.5in 4K iMac : 47.3 (higher is better)
  • 2.9GHz 21.5in iMac (late 2013) : 43
  • 2.7GHz 21.5in iMac (late 2013) : 37.2

We’re currently testing the iMacs to make a judgement on just how much better the Radeon Pro graphics card is compared to the Intel integrated card, but we envisage that there will be a significant difference.

For that reason, the Radeon Pro graphics card is another reason to pay the £200 extra to get the £1,249 3GHz Retina iMac.


As we have explained already, if you are deciding which 21-inch iMac to buy you might be wise to choose the 3GHz Retina version over the 2.3GHz non Retina model. It’s just £200 more.  However there is one other thing to factor in.

For years we have advised that if you are buying the iMac then you should upgrade to a Fusion drive rather than settle with the hard drive offered as standard on some models.

This year is no different – although the company is now offering the Fusion Drive as standard on more iMacs than ever.

Where the Fusion Drive used to be offered as standard only on the two more expensive 27-inch models, now the only models that don’t have a Fusion Drive are the non-Retina 21-inch and the entry-level Retina 4K model.

The Fusion Drive combines a small amount of flash with a hard drive. Certain things are kept on the SSD part of the drive so they can be accessed really quickly, but you also get a high capacity hard drive.

An iMac with a Fusion Drive will run a lot faster than one that does not have a Fusion Drive.

At just £90 as a build-to-order option, this is an affordable solution if you want the speed benefits of flash but can’t afford a large capacity SSD. We just wish it was standard across the range, but at least Apple has widened the range that do offer this solution.

So our advice if you are buying a 3GHz Retina iMac is to add on another £90 and get a Fusion Drive.

The standard storage offered in the 21-inch iMacs is as follows:

21.5in iMac

•    2.3GHz 1TB hard drive
•    3.0GHz 1TB hard drive
•    3.4GHz 1TB Fusion Drive

The Fusion Drive addition aside, it’s also good news that the SSD storage is now up to 50 percent faster, with write speeds of 3Gbps, according to Apple.

Ports and peripherals

As expected the new 21-inch iMac gained two Thunderbolt 3 ports, which doubles up as a USB Type-C port, which Apple describes as the “most powerful and versatile port ever.”

In addition to the Thunderbolt 3 ports you will also find the older USB port, so no need to worry about your older USB peripherals.

This latter point is definitely one in favour of the iMac in comparison with the MacBook Pro or MacBook, both of which have done away with the old USB standard in favour of USB-C/Thunderbolt 3.

One other change that makes us think Apple has been listening is the fact that you can now purchase a wireless keyboard with a number pad. This is something people have been requesting for years.


The new iMac pricing remains the same (or rather, pricing hasn’t changed since it changed in October).

Here’s how the pricing of the 21-inch breaks down:

•    2.3GHz i5, 1TB hard drive, 8GB RAM, Iris Plus 640, £1,049/$1,099
•    3.0GHz i5, Retina 4K, 1TB hard drive, 8GB RAM, Radeon Pro 555, £1,24/$1,299
•    3.4GHz i5, Retina 4K, 1TB Fusion Drive, 8GB RAM, Radeon Pro 560, £1,449/$1499
BTO options:
•    3.6GHz i5 processor + £180
•    16GB RAM + £180
•    32GB RAM + £540 (3.4GHz model only)
•    256GB SSD + £90
•    512GB SSD + £270
•    1TB SSD + £630


We think Apple has been listening to what people want and the new 21-inch iMac will answer a lot of people’s prayers. Sure we’d like the price of the entry-level model to be less, but even if it was we’d still be recommending that Apple’s customers should upgrade.

Unlike the MacBook Pro where the 13-inch model is less pro than its larger 15-inch sibling, there is a lot more in common between the 21-inch and 27-inch iMacs. It doesn’t feel like you need to buy a 27-inch model to get a decent Mac because the 21-inch is still pretty amazing.

The only thing it’s left us wishing is that the 21-inch iMac was a bit bigger. We’d love to see the return of the 24-inch iMac from the Intel switch days (although obviously with more modern specs!)

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