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Can a 21.5-inch iMac beat the latest-and-greatest M1 model in performance? Kinda
Extra performance wrung out, but we wouldn't rush to eBay
The benchmarks don't lie. Apple Silicon is fast. The M1 processor outperforms Intel’s competing i5 and i7 chips in virtually every metric you would care to mention, from CPU performance to graphics rendering. With that in mind, one may ask why anyone would want to buy an x86 Mac.
But as YouTuber Luke Miani recently showed, if you value your time cheaply, it's possible to make an old 21.5 inch iMac competitive with the latest-and-greatest wafer-thin M1 goodness. If you are a bit selective with the benchmarks, that is.
The hero of this tale is Apple's previous entry-level iMac. Released in 2019, this came (specs here) with a glacier-slow quad-core i3-8100 chip, paired with just 8GB of DDR4 RAM. It was not fast, but given its positioning as a tool for less-demanding home and education users, that wasn’t much of a problem. Miani said he acquired this for $750 — or two-thirds of the cost of a new M1 powered machine.
It was unambiguously outclassed by the M1 iMac, except for one thing: upgradability. Touting a socketed CPU, Miani was able to remove the sluggish i3-8100, replacing it with an octa-core Core i9-9900. This added $350 to the original purchase price.
Apple never actually offered the 21.5-inch iMac with an i9 chip. Those were saved for the larger 27-inch variant. According to EveryMac, a reliable compendium of Apple’s computing wares, the entry-level machine topped out with an i7-8700.
Rounding it off, Miani boosted the RAM from 8GB to 32GB, adding a further $150 to the cost. In total, the project cost $1,200 — just $50 short from the base M1 iMac with a seven-core GPU, 8GB RAM, and 256GB of internal storage.
Installing these upgrades proved to be a bit of a chore. As is the case with all iMacs released after 2006, the main avenue of ingress is through the display. Disassembly was further complicated by some awkwardly-located cables, which proved challenging to remove. This was necessary to replace the CPU, and, unlike previous models, switch out the RAM, which was contained within a metal cage affixed to the logic board.
So, was it worth it?
That largely depends on your perspective.
Are you particularly fussed about graphics performance? In that case, no. The stock M1 iMac utterly crushed the ageing AMD Radeon Pro 555X GPU found in 2019’s 21.5-inch variant. It simply wasn’t a fair fight.
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When using the Geekbench 5 Compute benchmark, which tests how the internal GPU copes with running games, image processing, and video editing, the 21.5-inch model scored 15,789 against the M1’s nearly 20,000.
But it shone when running CPU-driven tasks. When pitched against the CPU-heavy Cinebench R15 test, the custom 21-inch iMac beat the M1 by almost a third. Rendering a project in open source 3D creation suite Blender took half the time (although this likely wasn’t a fair test, given the absence of a native Apple Silicon build.) The M1 won on multi-core performance, but only just, with 100 points separating the two.
For the vast majority of users, the M1 iMac should be enough. And, of course, there is no guarantee that you will end up spending less. Apple, for instance, sells the same machine used in this video for a cool £1,059.99 refurbished. You can probably spend less on eBay, but that entails a level of risk that some might not be comfortable with.
Additionally, the long-term health of the Intel Mac is still very much uncertain. After it switched to x86, Apple only bothered to release one more system update for the PowerPC platform (namely: Mac OS X Snow Leopard). Developer support swiftly tapered off, particularly when it came to things like web browsers.
Still, if you already own one of these machines, Miani’s experiment shows it’s possible to squeeze extra performance beyond its original configuration. The 21.5-inch iMac also comes with a decent selection of ports, including USB-A and ethernet, making it slightly more practical.
This isn't Miani's first foray into iMac modification. As noted by this publication, he previously created one of the world's first custom M1 iMacs by shoving the innards of a Mac Mini into a broken 2011 27-inch iMac. ®