Apple 24in iMac (2021) M1 vs Apple 21.5in iMac (3.6GHz, 4-core, 2019 - now with SSD) full review

We've been waiting for Apple to redesign the iMac for a long time. The aluminium case of the Apple all-in-one was starting to look dated, having remained the same since 2009 when the 21.5in and 27in iMacs replaced the 20in and 24in iMacs. Apple has finally come up with the goods, revealing a brand new look for the smaller of the two iMacs. The 27in model is unchanged for now.

In this article we're going to examine what has changed in the new 24in iMac compared to the older 21.5in model. Apple is actually still selling one 21.5in iMac, but it has discontinued the other models. We would dissuade you from purchasing the still-on-sale 2.3GHz iMac for a number of reasons that we will go in to below, but you may still find the other 21.5in iMacs on sale from various stockists and in that case the decision isn't quite so clear cut.

This article will help you decide whether you should buy the old or the new iMac.

New vs old iMac price

We'll start of with the price, although right now you can't actually buy the 24in iMac. Pre-orders for the 24in iMac start on 30 April and it will go on sale in mid May, according to Apple, which is typically vague.

You will be able to pre-order the 24in iMac on Apple's website.

The pricing will be as follows:

  • 8-core CPU, 7-core GPU, 256GB SSD, 4.5K Retina display, two Thunderbolt/USB 4 ports, Magic Keyboard, £1,249 / $1,299/ AU$1,899
  • 8-core CPU, 8-core GPU, 256GB SSD, 4.5K Retina display, two Thunderbolt/USB 4 ports, two USB 3 ports, Magic Keyboard with Touch ID, £1,449 / $1,499/ AU$2,199
  • 8-core CPU, 8-core GPU, 512GB SSD, 4.5K Retina display, two Thunderbolt/USB 4 ports, two USB 3 ports, Magic Keyboard with Touch ID, £1,649 / $1,699/ AU$2,499

You can also buy the 2.3GHz dual-core iMac right now, but we strongly recommend that you don't do that. If you don't want to listen to us then by all means buy one from Apple or check our round up of the best iMac deals available.  Pricing for that is as follows:

  • 2.3GHz dual-core 7th-gen i5, 256GB SSD (was a 1TB HD), Intel Iris Plus Graphics 640, Non Retina £1,099 / $1,099 / AU$1,699
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The older iMacs that have now been discontinued offered the following specs. It is possible you will find a deal for one of these older iMacs (the best deals right now will appear below).

  • 3.6GHz quad-core 8th-gen i3, 256GB SSD (was a 1TB HD), Radeon Pro 555X, 4K Retina, £1,299 / $1,299/ AU$1,999
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  • 3.0GHz six-core 8th-gen i5, 256GB SSD (was 1TB Fusion Drive), Radeon Pro 560X, 4K Retina, £1,499 / $1,499 / AU$2,299
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You'll notice that in the UK the price of the new iMacs is £50 less than the previous equivalents, although it's not actually long ago that Apple raised the prices of iMacs £50 to put them in line with the US pricing. It's surprising, but great, that the company has reduced the UK prices back to where they were before the temporary bump. Hopefully it means that more Apple products will see a UK price drop soon.

New vs old iMac design

As discussed in Why I'm disappointed with Apple's 24in iMac design the new design of the 24in iMac makes the decision about whether to buy the 24in iMac will be a little bit more subjective than usual. You either will either like the new look or you will hate it.

New 24in iMac design

We think the problem is that the colour palette Apple is using for the new iMacs doesn't have wide appeal. Sure, you can choose from blue (above), green, pink, silver, yellow, orange and purple, but from the front of the iMac the colours are muted pastel shades of the bold hues on the back.

As a colleague lamented to us: why didn't Apple use the same bold colours on the front of the iMac? Perhaps these darker colour blocks would have wider appeal, but maybe the pale colours Apple chose will turn out to be popular. Like we said, it's subjective. There is always the safe silver option to choose from.

Red and Pink iMac

Our other criticism that we highlight in the article linked to above relates to the white border. If you placed a silver 24in iMac next to a 21.5in iMac the contrast in the borders might be the first thing you notice. The white borders of the 24in model are considerably narrower than the black borders on the 21.5in iMac. That's a definite benefit. The disadvantage is that if what you are looking at has a dark background - like a movie - then the edges of the screen will be very visible.

It's possible that the people destined to use the 24in iMac will be working on spreadsheets and word processors that have white backgrounds, and that their iMacs will be set against a white painted wall, in which case the opposite will be true and the white borders will disappear.

New iMac vs old iMac

If you don't like the design of the new iMac, or you want black boarders you have two choices. You can buy one of the now discontinued 21.5in iMacs before the stocks run out - check out our round up of the best deals. Or you can buy a 27in iMac.  But note, we have an inkling that when the successor to the 27in Mac arrives - hopefully later this year - it will have black borders and a darker colour scheme, but perhaps that is just wishful thinking.

New vs old iMac screen

The colour of the borders isn't the only thing you will notice when comparing the two generations of iMac.

Apple has been able to slim down the borders for the new iMac and as a result it is able to squeeze a bigger screen into a similarly sized frame.

Apple calls this the 24in iMac. You'd assume that meant the screen is 24in measured diagonally. You'd be wrong. We were disappointed to learn that the so-called 24in display is actually not 24in at all. The company admits in the footnotes that it is actually 23.5in measured diagonally.

The 21.5in iMac has a 21.5in display measured diagonally, just in case you were thinking maybe it just had a 21in display.

Ignoring the fact that Apple's decided to round up screen size this time, the new screen is a bonus. It offers 4,480 by 2,520 pixels, for what Apple calls 4.5K Retina. In comparison the 21.5in iMac offered 4,096 by 2,304 pixels for 4K Retina.

We should flag up the fact that the old £1,099/$1,099 21.5in iMac - which is still on sale - does not have a Retina display at all. Retina display is the phrase that Apple has used to described its screens since the introduction of the iPhone 4 in 2010. The term is supposed to describe a screen where the pixels are packed so closely together that they are imperceptible to the human eye at a distance of 12 inches. The magical pixel density is 326ppi - pixels per inch. Read: What is a Retina display for more information. The poor quality of the screen - which offers a measly 1920 by 1280 pixels - is one of the main reasons why we advise people against buying the cheapest 21.5in iMac.

24in iMac display

Another addition for the 24in iMac is True Tone. This technology - which is found on Apple's MacBooks, iPads and iPhones, and the 27in iMac, but was missing from the 21.5in iMac - "automatically adjusts the colour temperature of your display to the ambient light of your environment," as Apple puts is. This should mean that you get less eye strain and that the colours are more natural. It's a good reason to choose the 24in over the older models if you find one on sale.

Apple is also noting that the 24in iMacs have 500 nits brightness and wide colour P3 - but neither of these are new features compared to the older 4K iMacs (they don't exist on the non-Retina model though).

A final thing to mention here. We described the new and old iMacs as similarly sized above but that's not strictly true: the 2021 iMac is fractionally taller and wider than the older design, at x 54.7cm vs 45cm x 52.8cm. It is thinner at 14.5cm vs 17.5cm, though.

iMac dimensions:

  • 24in iMac: 18.1in (46.1cm) x 21.5in (54.7cm) x 5.8 (14.5cm)
  • 21.5in iMac: 17.7in (45cm) x 20.8in (52.8cm) x 6.9 (17.5cm)

New vs old iMac specs

Apple says that it has been able to slim down the iMac this much thanks to the M1 Chip which integrates the processor, graphics, memory, and more on one chip. More on the chip and other technology inside the iMac below.


As you can see there is a lot different on the surface, but what about the changes under the surface of the 2021 iMac? In many ways the changes you can't see are even bigger than those you can see on the 2021 iMac.

The biggest change is the inclusion of the M1 Chip - the Apple-made processor first introduced in November 2020 with the MacBook Air, MacBook Pro and Mac mini.

The M1 is a system on chip that combines the processor, graphics, RAM and other features on a single chip. Apple credits the M1 for making it possible for the iMac to slim down to 14.5cm from 17.5cm, although there is a lot more to the M1 than space saving.

We'll start off with the processor component. Apple's M1 processor has 8-cores. Four of these are described as being for performance and four are for efficiency. This is the same processor as seen in the MacBook Air that we reviewed last year, so we have a good idea what to expect from it.

The good news is that the M1 is already proven to be outstanding. When we ran the Geekbench benchmark when it came to multi-core processing the M1 was miles ahead (at 7,584), and not just in comparison to the Intel processor in the older MacBook Air (3,294), but also faster than the quad-core 2.0GHz processor in the 2.0GHz i5 MacBook Pro (4,504).


Unfortunately we don't have the Geekbench 5 results for the 2019 21.5in iMac with their 8th generation Coffee Lake processors because we used the older Geekbench tool when we reviewed that machine. See: 2019 21.5in iMac review. That does make comparisons difficult, but we do have the score for the 9th generation 2.3GHz 8-core i9 in the 16in MacBook Pro (7,346) and as you can see the M1 even beat that! It will certainly be interesting to see how the new 24in iMacs compare with the older iMac models, that offered up to 3.2GHz 6-core 8th-gen Core i7-8700 as a build-to-order option.

The old iMac models featured Intel's 9th generation Coffee Lake processors at up to 6-cores, here's what was on offer:

  • 3.6GHz quad-core Intel Core i3
  • 3.0GHz 6-core Intel Core i5
  • 3.2GHz 6-core Intel Core i7

It seems likely that the M1 processors will beat these 2019 Intel processors. Apple claims "up to 85 percent faster CPU performance." It also indicates that users can expect apps like "Xcode and Affinity Photo to compile code in a fraction of the time" and be able to "fly through edits in Adobe Lightroom and easily work with massive 100-megapixel images."

Despite the promise of the M1, our biggest disappointment is that the M1 Chip has been used for the iMac rather than the rumoured M1X, which is expected to offer more processor cores, and crucially more graphics cores.


We have high hopes for the processor part of the M1, but when it comes to the graphics things are a little less clear. This is because the 21.5in iMac range featured discreet graphics cards (with the exception of the entry-level model). The M1 integrates the graphics onto the same card as the processor. Generally discrete graphics are considered superior to integrated graphics.

The main difference between discrete and integrated graphics is the fact that integrated graphics share the RAM with the processor, while discrete graphics have their own separate RAM. As we will explain in more detail in the RAM section, the RAM in the M1 Chip features on the same chip as the GPU and CPU, so the graphics and processor can share a direct connection to it. This should mean that Apple's graphics solution is already superior to Intel's integrated graphics.

In fact Apple claims up to two times faster graphics performance than standard 21.5‑inch iMac models.

The GPU in the M1 is available in either 7-core or 8-core options.

The 21.5in iMac had the following options:

  • AMD Radeon Pro 555X with 2GB of GDDR5 memory
  • AMD Radeon Pro 560X with 4GB of GDDR5 memory
  • AMD Radeon Pro Vega 20 with 4GB of HBM2 memory

As with the processor, we do already have a bit of insight, not just into how well these M1 graphics options perform compared to other Intel graphics, but also the difference you can expect if you choose the 8-core option over the 7-core option, that being one of the biggest points of difference between the two 24in iMacs.

We were able to run graphics tests on both M1 MacBook Air models - the 7-core GPU and the 8-core GPU. We ran the Geekbench graphics test as well as the Cinebench graphics. In the Geekbench Compute Metal test the 8-core GPU scored 20,960 while the 7-core GPU scored 19,283. However, we should be able to see an even better score from the iMac thanks to the cooling features that the MacBook Air lacks. It's interesting to note that the GPU In the M1 MacBook Pro scores 21,842, which should be closer to the score we will see in the 24in iMac.

Crucially these graphics tests show that the 16in MacBook Pro with discrete graphics performed much better than the M1 Macs. It's likely that this will continue to be the case when the 16in MacBook Pro and the 27in iMacs are compared to the 24in iMac. This is why we would have liked to see the M1X Chip with the 24in iMac, because we expect more graphics cores with the newer chip. Apple is said to be working on a 16-core GPU. It's likely we will see this with the 27in iMac when Apple updates it.

iMac games

RAM and Storage

As mentioned above, one of the benefits of the M1 Chip is that it incorporates the RAM onto the SoC. On the M1 Chip the graphics card and CPUs share common memory that both can access directly at all times - so, for example, the CPU and GPU can access the same photo in memory during a task and process it faster. Apple calls this Unified Memory Architecture. In contrast the Intel graphics solution shares memory with the CPU, but when it is being used by the GPU it is no longer available to the rest of the system.

All this should mean M1 Macs can access data much quicker. It should also mean that 8GB is sufficient.

The only real problem with the RAM is that because it is part of the M1 chip it will not be possible to update it at a later date, so if you think you might need more RAM in the future then get it at point of sale: 16GB RAM the maximum amount of RAM available as a build to order option. This contrasts with the option for 32GB RAM in the 21.7in 4K iMac. It might seem like a backwards step that the new iMac doesn't offer as much RAM, but the new architecture should mean that you don't need it.

The iMac with 7-core GPU offers offers up 256GB SSD as standard and up to 1TB SSD storage, while the two iMacs with 8-core GPU offer 256GB or 512GB as standard, and up to 2TB SSD. The 21.5in iMac only offered 256GB as standard and up to 1TB SSD.

New vs old iMac features

Those are some great additions to the new iMac, but are other new features that are just as impressive.

First up we have one that we have been awaiting for far too long - an improved FaceTime camera.


The FaceTime camera on the Mac has come under fire for being so poor, something exacerbated by the pandemic, with so many usually office-based workers suddenly being required to attend meetings via their web cam.

It's excellent news, therefore, that the FaceTime camera in the new 24in iMac is a huge improvement. Where previously Apple included a FaceTime HD camera, now in its place is a 1080p FaceTime HD camera with double the resolution. That's not all: it features a larger sensor captures more light and it takes advantage of the advanced image signal processor (ISP) in the M1 to enhance image quality. Here technology like the Neural Engine component of the M1 comes into play as it is able to make intelligent exposure and white balance adjustments to the image. The new FaceTime camera should make you look presentable in meetings and family video calls alike.


It's not only the FaceTime camera that makes for better video calls. The 24in iMacs also boast improved audio with mics that are designed to reduce feedback and beamforming technology so that the mics can ignore background noise.

The new audio capabilities are a big deal for the new iMac models. Where the old model had stereo speakers the new iMac has two pairs of force-cancelling woofers, each balanced with a high-performance tweeter. This high-fidelity six-speaker system should offer wide stereo sound as well as support for spatial audio when playing video with Dolby Atmos.

Ports & Peripherals

There's one last thing that can't go unmentioned: the new iMac keyboard. Depending on which iMac you buy the so-called Magic Keyboard comes with either a Lock Key or Touch ID.

With Touch ID on the new Magic Keyboard it will be possible to unlock the Mac and use Apple Pay to pay for things just by tapping the Touch ID button.

The entry level 7-core GPU 24in iMac comes with a Magic Keyboard with Lock Key as standard, but you will be able to configure it with a Touch ID sensor. The two 8-core GPU models ship with the Magic Keyboard with Touch ID as standard. More information: Magic Keyboard with Touch ID: how to buy, price and specs.

The keyboard itself is colour-matched to the iMac, as are the mouse and, if you choose one, the trackpad. Magic Keyboard also offers keys for Spotlight, Dictation, Do Not Disturb, and emoji.

New iMac keyboard

The Magic Keyboard, mouse and trackpad are all wireless, as you would expect in this day and age. If you are concerned about the ports available to you here's what's on offer:

The entry-level 24in iMac offers two Thunderbolt/USB 4 ports. If you are after USB 3 (which is backward compatible with the older USB A) then only the 8-core GPU iMac offers two USB 3 ports in addition to the two Thunderbolt/USB 4 ports.

The entry-level 24in iMac also lacks Gigabit Ethernet, unless you configure it at point-of-sale. The other 24in models and the older 21.5in model do come with Gigabit Ethernet - interestingly this is actually built into the power brick of the new 24in iMac.

A final disappointment for those longing for an SDXC card slot in the new iMacs: there it none. Only the older 21.5in iMacs offer the SDXC card slot. Those Macs offered Two Thunderbolt 3 (USB-C) ports, Four USB-A ports, and Gigabit Ethernet. If you want these features they are of course still available on the 21.5in iMac that Apple is still selling, but like we said at the beginning of this article, you really shouldn't buy that model.


We're withholding judgment on the design until we see the new iMac in the flesh, but we have very high hopes for what's on the inside and we are not only glad but also relieved to hear of the FaceTime camera improvements. When we have run benchmarks we will have a better ides of the new processor and graphics capabilities, which should match, and potentially beat the capabilities of the other M1 Macs.

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