How fast are the "2020" 27-Inch iMac models compared to one another? How fast are they compared to the "2019" iMac models and the iMac Pro?

Please note that the "2019" and "2020" iMac models and iMac Pro models all have been discontinued. However, this Q&A still can be quite helpful to anyone buying or selling one of these systems on the used market.

In the corporate press release for the "2020" 27-Inch iMac, Apple uses the word "performance" a whopping thirteen times including a promise of "much faster performance" in the subtitle. With such emphasis, it is apparent that the performance increase of the "2020" lineup over its predecessors should be significant.

Photo Credit: Apple, Inc. (27-Inch "2020" iMac 5K Model)

With a more advanced architecture, processors, and graphics processors, it would be a safe bet that the "2020" 27-Inch iMac models are faster than the "2019" 27-Inch iMac models replaced in addition to the rather vintage entry-level iMac "Core i5" 2.3 21.5" (Mid-2017) and "2019" 21.5-Inch iMac models that Apple still sells as new.

Apple's press release even quantifies some of the performance boost of the "2020" 27-Inch iMac compared to the eight-core iMac -- the iMac "Core i9" 3.6 27-Inch (5K, 2019) -- from the year before:

• Up to 65 percent more plug-ins in Logic Pro X.
• Up to 40 percent faster 8K ProRes transcode in Final Cut Pro X.
• Up to 35 percent faster rendering with Arnold in Autodesk Maya.
• Up to 25 percent faster build time in Xcode.

It is worth noting that this showdown even is comparing the highest-end configure-to-order models from both lines instead of the fastest configure-to-order "2020" iMac to an entry-level "2019" iMac, a demonstration of Apple's confidence regarding the performance increase.

Nevertheless, this is not comparing the full range of iMac models, nor does it compare the "2020" 27-Inch iMac models to each other or to the iMac Pro, so independent benchmarks still can be quite helpful for a broader perspective.

General Performance Overview

For a general overview of overall performance between the "2020" iMac models and earlier Mac desktops and notebooks alike, EveryMac.com's own Ultimate Mac Comparison makes it quick to compare side-by-side Geekbench benchmark averages with all other G3 and later Macs for thousands of possible performance comparisons.

For example, for the "2020" 27-Inch iMac models compared to one another, the Geekbench 5 benchmark shows that the entry-level "2020" 27-Inch iMac -- the iMac "Core i5" 3.1 27-Inch (5K, 2020) -- only is 2% slower in single-core tasks and 4% slower in multicore tasks than the next level up -- the iMac "Core i5" 3.3 27-Inch (5K, 2020), but a more significant 8% slower in single-core tasks and 27% slower in multicore tasks than the high-end stock model -- the iMac "Core i7" 3.8 27-Inch (5K, 2020) -- which has a faster clockspeed and two more cores.

For those interested in the fastest possible "2020" iMac, Geekbench 5 shows that the custom configured iMac "Core i9" 3.6 27-Inch (5K, 2020; 5700/XT) -- which is equipped with both a custom processor upgrade and custom video processor upgrade for the standard high-end iMac "Core i7" 3.8 27-Inch (5K, 2020) -- is 3% faster in single core tasks and 16% faster in multicore tasks. Of course, for someone who wants maximum performance at any price, the processor upgrade is still worth considering regardless, but because the processor upgrade alone costs 17% more (US$400), it is the best value for someone who has software that can take maximum advantage of the multicore processor.

"2019" 27" iMac vs. "2020" 27" iMac Performance

The Geekbench 5 benchmark shows that the "2020" 27-Inch iMac models are faster across the board than the "2019" models each replaced:

2019 27" iMac	2020 27" iMac	Single Core	Multicore
"Core i5" 3.0 27" 5K	"Core i5" 3.1 27" 5K	+12%	+17%
"Core i5" 3.1 27" 5K	"Core i5" 3.3 27" 5K	+9%	+15%
"Core i5" 3.7 27" 5K	"Core i7" 3.8 27" 5K	+8%	+43%
"Core i9" 3.6 27" 5K	"Core i9" 3.6 27" 5K	+2%	+8%

However, when comparing each 27" iMac model to its immediate replacement, the Geekbench 5 benchmark does not show a performance increase as dramatic as Apple's selected software examples.

"2017/2019" 21.5" iMac vs. "2020" 27" iMac Performance

The Geekbench 5 benchmark shows a much more substantial difference between the older, but still current 21.5" iMac models and their newer 27" contemporaries:

2017/2019 21.5" iMac	2020 27" iMac	Single Core	Multicore
"Core i5" 2.3 21.5"	"Core i5" 3.1 27" 5K	+32%	+179%
"Core i3" 3.6 (4K)	"Core i5" 3.3 27" 5K	+26%	+81%
"Core i5" 3.0 (4K)	"Core i7" 3.8 27" 5K	+21%	+64%
"Core i7" 3.2 (4K)	"Core i9" 3.6 27" 5K	+7%	+44%

It should come as no surprise that the most substantial performance difference is at the low-end between the much older entry-level 21.5-Inch iMac -- the iMac "Core i5" 2.3 21.5" -- first introduced in 2017, but still sold as new and the entry-level "2020" 27-Inch iMac. Of course, the entry-level "2020" 27-Inch iMac costs 64% more (US$700), but it is a much better value relative to its performance, especially in multicore tasks.

"2020" 27" iMac vs. iMac Pro Performance

For the "2020" 27-Inch iMac models compared to the older, but still current "Late 2017" iMac Pro models, the Geekbench 5 benchmark solidly demonstrates that the non-Pro iMac 27" models, particularly ones with faster clockspeeds, are faster in single core tasks than the iMac Pro, but much slower in multicore tasks because the iMac Pro models have many more cores:

2017 iMac Pro	2020 27" iMac	Single Core	Multicore
"8-Core" Xeon 3.2	"Core i5" 3.1 27" 5K	+5%	-30%
"10-Core" Xeon 3.0	"Core i5" 3.3 27" 5K	+2%	-38%
"14-Core" Xeon 2.5	"Core i7" 3.8 27" 5K	+12%	-31%
"18-Core" Xeon 2.3	"Core i9" 3.6 27" 5K	+15%	-34%

Most users with software that isn't optimized for multiple cores will get faster performance on the non-Pro iMac, whereas those with high-end professional software designed to take full advantage of multiple cores will get more performance out of the iMac Pro.

Performance Summary

Ultimately, the "2020" iMac models provide a notable speed boost compared to their predecessors, and Apple's promoted speed increases are reasonable, but to maximize the performance gain, it is clear that you will need to be using properly optimized software that can take full advantage of the multicore processor and high-end configure-to-order graphics processor.

For most users, the "2020" 27-Inch iMac models definitely are a better value than the barely upgraded "2019" 21.5-Inch iMac models as well as the aging and expensive iMac Pro line. However, the iMac Pro still is quite a bit faster in multicore tasks.

Given even lower discount prices on the used market, and still solid performance -- particularly in single-core tasks, the earlier "2019" 27-Inch iMac models remain well worth consideration, also.

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