I began by asking each Mac to bounce a dense Logic Pro X project to a 16-bit AIFF stereo track. The Mac Pro accomplished the job in 50 seconds. The Retina iMac took 1 minute 12 seconds, and the older iMac, 1 minute and 29 seconds.
I then imported into Final Cut Pro X a five minute 1080p clip, bumped up the clip's volume by five points, applied three effects to it (50s TV, Vignette, and Super 8mm), and exported it as a 720p video using the Apple ProRes 422 codec. The Mac Pro did the job in 54 seconds, the Retina iMac finished in 1 minute and 9 seconds, and the 2012 iMac accomplished the task in 1 minute and 30 seconds.
(Previous to this, I exported the same clip with effects using Final Cut Pro's Apple Device 720p preset. In this case each iMac outdid the Mac Pro, with the Retina iMac doing the job in 1 minute and 26 seconds, the older iMac in 1 minute and 47 seconds, and the Mac Pro coming in last at 2 minutes and 31 seconds. This can be explained by the iMacs taking advantage of Intel QuickSync Video, which allows i5 and i7 Macs to render H.264 video more quickly than can Macs with Xeon processors.)
To hit each Mac as hard as I could, I then ripped the Maximum Movie Mode track from the Blu-ray disc of 2009's Sherlock Holmes and ran the resulting .mkv file through HandBrake, using the Apple TV 3 preset. It took the Mac Pro 1 hour and 36 minutes, the Retina iMac finished second at 2 hours and 24 minutes, and the older iMac pulled up the rear at 2 hours and 53 minutes. During this process the Retina iMac's fan came on about four minutes into the process and didn't stop until the job was complete. The older iMac's fan, however, remained quiet throughout.
Given the results of these tests, it's pretty clear that for tasks that take advantage of a processor's multiple cores, the Mac Pro remains the champ. And for a computer that costs $1,500 more than the Retina iMac, it should. That said, in regard to single-core tasks, the Retina iMac appears to be the faster machine. So while well-heeled audio, video, and image professionals may not prefer the Retina iMac, typical users will. And, after all, that's the primary point of today's iMac--a computer powerful (and beautiful) enough for just about everyone.
The bottom line
The iMac with Retina 5K display has a lot going for it. The display is gorgeous, at $2,500 it's like getting a free computer with your high-resolution display, it has enough ports to please all but the most demanding user, it won't jack up your power bill, and it's no slouch when it comes to performance. Apple should be proud to have made such a thing. You'll be just as proud to own one.
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