How fast are the "2019" iMac models compared to one another? How fast are they compared to the "Mid-2017" iMac models and the iMac Pro?

Please note that the "2019" iMac models 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 company press release for the "2019" iMac, Apple's headline is "iMac gets a 2x performance boost," so it is a safe bet that the performance increase is significant at least with specific tests.

Photo Credit: Apple, Inc. (27-Inch "2019" iMac 5K Model)

The "2019" iMac models pack more advanced processors, architectures, and graphics processors, so it would be expected for these models to be faster than the "Mid-2017" iMac line that they mostly replaced.

However, just how much faster the "2019" iMac models are than earlier systems -- as well as how fast they are compared to the more expensive iMac Pro -- requires independent benchmarks and real-world testing rather than just relying on the hyperbole of any company's marketing department.

General Performance Overview

For a general overview of overall performance between the "2019" 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 "2019" iMac models compared to one another, the Geekbench 4.0 benchmark shows that the least expensive 21.5-Inch iMac 4K model -- the iMac "Core i3" 3.6 21.5" 4K (2019) -- is 12% slower in single-core tasks and 35% slower in multicore tasks than the next level up -- the iMac "Core i5" 3.0 21.5" 4K (2019) -- which supports Turbo Boost for a higher maximum clockspeed and has two more processor cores.

However, the entry-level 27-Inch 5K model -- the iMac "Core i5" 3.0 27" 5K (2019) -- is effectively the same speed as the iMac "Core i5" 3.0 21.5" 4K (2019) because both are equipped with the same processor and architecture, although the 27-Inch 5K model does have a modestly more capable graphics processor to drive the larger display.

For those interested in the fastest possible "2019" iMac, Geekbench 4.0 shows that the custom configured iMac "Core i9" 3.6 27" 5K (2019) -- which is a US$400 upgrade option for the standard high-end iMac "Core i5" 3.7 27" 5K (2019) -- is 7% faster in single core tasks and 42% 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 it costs 17% more, it is the best value for someone who has software that can take maximum advantage of the multicore processor.

"Mid-2017" iMac vs. "2019" iMac Performance

The Geekbench 4.0 benchmark shows that the "2019" iMac models are faster across the board than the two year old systems they replaced, but the performance increase is much more substantial in multicore tasks and increases more dramatically toward the high-end of the lineup, in particular:

2017 iMac	2019 iMac	Single Core	Multicore
"Core i5" 3.0 21.5" 4K	"Core i3" 3.6 21.5" 4K	+2%	+3%
"Core i5" 3.4 21.5" 4K	"Core i5" 3.0 21.5" 4K	+12%	+50%
"Core i7" 3.6 21.5" 4K	"Core i7" 3.2 21.5" 4K	+11%	+51%
"Core i5" 3.4 27" 5K	"Core i5" 3.0 27" 5K	+10%	+49%
"Core i5" 3.5 27" 5K	"Core i5" 3.1 27" 5K	+8%	+47%
"Core i5" 3.8 27" 5K	"Core i5" 3.7 27" 5K	+12%	+51%
"Core i7" 4.2 27" 5K	"Core i9" 3.6 27" 5K	+10%	+70%

The low-end non-4K "Mid-2017" iMac model that lingered for years as a new option -- the iMac "Core i5" 2.3 21.5" (Mid-2017) -- is only 2% slower in single core tasks but 30% slower in multicore tasks than the slowest "2019" iMac 4K model -- the iMac "Core i3" 3.6 21.5" 4K (2019).

"Late 2017" iMac Pro vs. "2019" iMac Performance

For the "2019" iMac 5K models compared to the "Late 2017" iMac Pro, the Geekbench 4.0 benchmark solidly demonstrates that the non-Pro iMac 5K 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	2019 iMac	Single Core	Multicore
"8-Core" Xeon 3.2	"6-Core" i5 3.0 27" 5K	+3%	-33%
"10-Core" Xeon 3.0	"6-Core" i5 3.1 27" 5K	+3%	-39%
"14-Core" Xeon 2.5	"6-Core" i5 3.7 27" 5K	+12%	-45%
"18-Core" Xeon 2.3	"8-Core" i9 3.6 27" 5K	+20%	-32%

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.

Other Benchmarks & Real-World Test Results

Geekbench benchmarks provide a good overview of overall performance, but additional benchmarks and real-world tests also can be useful, particularly for graphics-related tasks.

For example, Macworld tested the higher end iMac 4K model -- the iMac "Core i5" 3.0 21.5" 4K (2019) -- customized with a faster AMD Radeon Vega 20 graphics processor (+US$350) and determined:

The Vega 20 provides a significant boost over the Radeon Pro 560. In the OpenCL test, the new iMac and its Vega 20 was 41 percent faster than the 2017 iMac and its Radeon Pro 560. In the Metal test, the new iMac was 36 percent faster.

BareFeats tested the highest of the high-end iMac 5K models -- the iMac "Core i9" 3.6 27" 5K (2019) -- also customized with the faster AMD Radeon Vega 48 graphics processor (+US$450) and concluded that "the Pro Vega 48 should be 32% to 118% faster than the [default AMD Radeon] Pro 580X."

Finally, AppleInsider hit the entry-level iMac 4K -- the iMac "Core i3" 3.6 21.5" 4K (2019) -- the entry-level iMac 5K -- the iMac "Core i5" 3.0 27" 5K (2019) -- and the maxed out high-end iMac 5K -- iMac "Core i9" 3.6 27" 5K (2019) further upgraded with the AMD Radeon Vega 48 graphics processor -- with the Cinebench R20 benchmark and reported:

[The high-end custom configuration] earned a 4108. That easily beat out the iMac 5K base score of 2383, which itself was well above the 1472 we earned on the base iMac 4K.

In percentage terms, this means that the Cinebench R20 benchmark found the entry-level iMac 5K to be 62% faster than the entry-level iMac 4K and the high-end custom-configured iMac 5K to be a whopping 72% faster than the entry-level iMac 5K.

Performance Summary

Ultimately, the "2019" iMac models provide a significant speed boost compared to their predecessors in overall performance and graphics performance, particularly in multicore tasks. To get a "2x performance boost" from a "2019" iMac over the "Mid-2017" iMac line, though, it is clear that you will need to be using heavily optimized software that can take full advantage of both the multicore processor and the high-end custom configured graphics processor.

The "2019" iMac models tend to be about the same speed or even faster than the iMac Pro in single core tasks, but much slower in multicore ones.

Given discount prices, and still solid performance in single core tasks, the "Mid-2017" iMac models remain well worth considering, too.

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