Tuesday, January 2, 2018 [Tweets] [Favorites]

iMac Pro Performance

Jason Snell:

One of my most common audio workflows involves grabbing audio files from panelists, converting them to WAV format via the ffmpeg command line tool, removing background noise via iZotope RX 6’s Spectral Denoise filter, writing that file back to disk, and using the private-beta tool sidetrack to sync the panelist’s file up with a reference track. There’s a lot of processor-intense stuff in there, as well as some disk access.

It took my 2014 5K iMac 160 seconds to perform all of those tasks; it took the iMac Pro 96 seconds, meaning that the iMac Pro was able to do the job in 60 percent of the time. Isolate just the processor-intensive task of denoising three hours of audio, and the 5K iMac took 94 seconds, versus 49 seconds for the iMac Pro—a little more than half the time.

I frequently take large 1080p videos export from editing apps and slim them down into versions I can upload to YouTube or post for a video podcast via the HandBrake video-encoding app. I performed one of these encodes on both the 2014 5K iMac and the iMac Pro; the 5K iMac encoded the video in 21 minutes and 16 seconds, while the iMac Pro took 11 minutes and 14 seconds. Once again, that’s a little more than half the time. It’s enough for me to declare that for jobs optimized for multiple processor cores, this base model iMac Pro is nearly twice as fast as the top-of-the-line 5K iMac from 2014.

Max Yuryev (via Václav Slavík):

After the second test, each additional run would cause the iMac Pro to slow down the CPU when the temperature reached roughly 94C, which caused the clock speed to drop from 3.9ghz to about 3.6ghz for a second or two. This allowed the CPU to drop below 92C, and the clock speed to rise back to the maximum turbo boost of 3.9GHz.

Interestingly, even after 10 consecutive benchmarks, the iMac Pro fans were barely audible. Instead of ramping up the fan speed to keep the CPU at its maximum turbo boost speed, the iMac Pro just kept the cycle going, with the clock speed dipping every 10 seconds or so while staying very quiet.


With that said, it is a bit disappointing to see Apple prioritize noise over performance and thermals on a high-end pro machine.

Ben Cunningham:

I’ve been trying out an iMac Pro for FCPX editing and have been really disappointed with the performance. This review confirms it: in many cases, the iMac Pro performs WORSE than this year’s iMac[…]

I can also confirm this reviewer’s findings: the CPU and GPU are seriously underutilized when dealing with any common formats, like H264 or ProRes. The Pro only starts to show an advantage when dealing with H265/Raw/8k formats.

rob-ART morgan:

In this article we highlight CPU and GPU performance of the ‘low end’ iMac Pro (with optional GPU) compared to two popular Mac Pro configurations and the fastest iMac 5K.


Apple did its homework when planning the iMac Pro. As you can see from the results above, it beat both beefy Mac Pros in CPU performance. And if we had not jury-rigged an RX Vega 64 in the 2010 Mac Pro tower, it would have won 3 out of the 4 GPU contests.

On the other hand, maybe the fact that an 8-year-old Mac Pro with an updated GPU can beat a current iMac Pro means that GPUs should be upgradeable.

Previously: The iMac Pro.

Update (2018-01-02): See also: iMac Pro Teardown.

Update (2018-01-03): Tuomas Artman:

First iMac Pro tests indicate that you’ll get almost no Swift Xcode compilation performance gains compared to a recent MBP.

Daniel Martín:

Assuming a good benchmark test, this is not very surprising. Parallelism is only exploited at the later stages of compilation; SIL generation, importing, and type checking never run in parallel, for example. Using WMO also exploits parallelism worse.

Troy Gaul:

Decided to do a few Xcode build timings of the iMac Pro. It’s about twice as fast as my [2016] 15” MacBook Pro.

Average full build times for Linea (simulator, debug build):

  • iMac Pro (3 GHz 10-core, 64GB): 17.76 sec
  • MacBook Pro (2.9 GHz 4-core i7, 16GB): 33.14 sec

A bit of context: Linea is written in Swift (about 200 .swift files of varying sizes) and only includes a little Objective-C and few dependencies. Build times were done in the Xcode app after cleaning twice (to avoid pre-build and indexing).

Update (2018-01-08): Steven Frank:

Very unscientific benchmark: re-encoding a 12m WMV video to MP4 with ffmpeg -- Mac Pro 2010 (12 core) 5:54 -- Mac Pro 2013 (6 core) 6:57 -- iMac Pro (10 core) 3:21

Nothing surprising, but I was surprised how much I'd future-proofed myself by buying a 12-core Mac in 2010. iMac Pro10-core is almost but not quite 2x as fast. Still trying to convince myself to hold off until the mythical modular Mac is revealed.

See also: Lloyd Chambers.

Oliver Peters (via Hacker News):

After all of this testing, one is left with the answer “it depends”. The 2013 Mac Pro has two GPUs, but not every application takes advantage of that. Some apps tax all the available cores, so more, but slower, cores are better. Others go for the maximum speed on fewer cores. All things considered, the iMac Pro performed at the top of these three machines. It was either the best or close/equal to the best. But, this is an incremental difference in the 10% to 30% range. But, of course some of these numbers will be meaningful and others won’t, depending on the apps used and a user’s storage situation.

Update (2018-01-11): See also: Lloyd Chambers.

Update (2018-01-12): James Thomson:

Rough first benchmark - doing a full build of PCalc in Xcode on this iMac Pro takes around 56s, compared to 92s on my 1st gen iMac Retina 4Ghz i7. Less of an improvement than I would have hoped to see for having six more cores, if I’m being honest.

See also: Accidental Tech Podcast.

Update (2018-01-17): Mark Bernstein:

The new iMac Pro builds Tinderbox from scratch in 30sec — about 6x my trusty MacBook Pro 15. In other respects, it’s just fast, but for compiling and running code, it’s blazing.

Update (2018-02-27): Orta Therox:

Interesting that it’s the Hackintoshes that are at the top of @ashfurrow’s Xcode Hardware Performance charts.

Update (2018-03-30): Peter Steinberger:

iMac Pro builds our project almost twice as fast as a 2015y iMac. (6 minutes. Maxed Mac Mini takes around 30)

1 Comment

Someone recently got macOS running on a 2.3 GHz 4 processor AMD Opteron machine with 64 cores.


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