The Retina iMac and its 5K display… as a gaming machine? [Updated]

From 5k to 4k

The first thing I noticed upon booting up in Windows 8.1 is that Windows does not run at the display’s native 5120x2880 resolution. When I logged on, I was greeted by a desktop running at 3840x2160, one of a number of different resolutions commonly lumped under the "4k" banner (this particular 4K flavor is usually referred to as "Ultra HD").

Interestingly, the non-native resolution didn’t exhibit any visible scaling artifacts. The high pixel density seems to more than make up for the loss of resolution from "5K," and the display blends the 8,294,400 points yielded by 3840x2160 into the native 14,745,600 pixels quite smartly. Even sitting with my nose an inch or so away from the screen—a distance my mother assured me when I was younger would ruin my eyes—I couldn’t see any feathering or blurring around edges and lines. Type remained sharp, and everything looked crisp.

Windows 8.1 does an admirable job of taking advantage of the display’s high DPI, proving we’ve come a long way since the dark days of Windows XP’s terribly broken DPI slider. However, unlike OS X’s strict high DPI adaptations, many third-party Windows applications don’t fare as well as Windows and Microsoft’s first-party stuff. Steam in particular looked like a scaled-up blurry mess. Then again, Steam has always been a graphical disaster, eschewing common sense for its own insane ideas of how a window should look.

Update: Here's the GPU-Z output, showing the reported details on the Radeon R9 M295X. As expected, the GPU is an AMD Tonga, running at 850MHz:

Before jumping into any games, I installed the 3DMark benchmark tool and ran the standard benchmark test suite, comparing the results to a set of benchmark runs on my 2013 iMac:

I admit that I was surprised. The Retina iMac’s Radeon R9 M295X put up perfectly cromulent numbers—far higher than my suddenly very sad-looking 2013 iMac.

Update: Here's an additional test result, showing the performance of 3DMark's "Fire Strike Ultra" 4K benchmark:

The next test was to actually, you know, game on the thing. Having recently finished off Alien: Isolation, I decided to take that title for a 4K spin. Current-gen consoles reportedly have some trouble keeping that title running at its target of 30 frames per second at a mere 1920x1080 resolution, so it seemed like the perfect test for our Mac. (Plus, I'll admit I'm kind of giddy at the idea of spanking both the XBox One and the Playstation 4 with an iMac.)

Alien: Isolation has a built-in benchmarking mode on PC that can be enabled simply by adding benchmark to the game’s startup options, so the first thing I did was enable this on both the 2013 iMac and the Retina iMac and fire it up. The benchmark runs on a preset loop, so first I ran it with identical settings on each iMac (2560x1440 resolution, 8x Anisotropic filtering, SMAA T2x antialiasing, and "ultra" settings for shadows, textures, and other details), and then again on the Retina iMac with the same settings but at 3840x1440 resolution. Each benchmark was run three times, and these are the averages:

The 3840x1440 runs appeared visually smooth when I watched them complete, but the numbers tell a bit of a different tale. When I hopped into the game to actually play at that resolution, there was a noticeable amount of mouse lag. Indications are that a faster CPU would have helped considerably, but with the iMac, what you get is what you get.

However, dialing the resolution down to 2560x1440 on the Retina iMac resulted in an extremely slick playing experience. I blew through the Crew Expendable DLC module (which famously brought together Alien actors Veronica Cartwright, Yaphet Kotto, Tom Skerritt, and Sigourney Weaver to re-voice their roles from the 1979 film) in that resolution and the gameplay was buttery smooth, without any trace of stutter.

After that, I kicked the resolution back up to 4K to take some screenshots and wander around the Nostromo’s upper deck. If there’s one thing Alien: Isolation does superbly well, it’s capture the look and feel of Ridley Scott’s 1979 movie. The game oozes picture-perfect 1970s retro-futurism, and in 4k, it looks positively beautiful.

Preliminary judgment: it games!

I’ll be putting the iMac through some more evaluations in the coming days, including hooking my Oculus Rift DK2 up and trying out some Elite: Dangerous after that particular game’s latest beta release goes live on October 28. However, just based on the performance of Alien: Isolation, any fears prospective Retina iMac owners might have had that the system’s high resolution will outstrip the GPU’s ability to keep it fed appear to be unfounded.

Games at 2560x1440 (or "1440p," if you prefer) look and run great, even with AA and AF enabled. The fact that the GPU is scaling the image up to fit to the underlying 5K pixel grid really doesn’t appear, at least to my eye, to yield any of the blurriness that you get when using non-native resolutions on lower-DPI LCDs. One game and some first impressions does not equal a total assessment, but at least at first blush, buying a Retina iMac isn't going to mean you have to log out of Steam and never come back again.

There are certainly issues with the Retina iMac—at least for now, you can’t connect an external 5K display to it, due to the fact that the bandwidth required to push more than 14 million pixels outstrips the available bandwidth on a DisplayPort 1.2 connection. Similarly, the Retina iMac doesn’t support being used as a 5K display in Target Display Mode. The base configuration’s Fusion Drive doesn’t let you install Windows on the SSD, so Boot Camp excursions will have to chug along at plain old hard disk drive speed. And, of course, it costs $3,000—for that amount of money, you can part together one hell of a gaming PC.

Still, I’d be lying if I said that I didn’t want one now. I’ll be playing the hell out of my Steam library on the thing over the next week before I have to send it back. Peter Bright is already spitting rage at me in the Ars staff IRC channel that I didn't benchmark with Battlefield 4 or Far Cry 3 (simple explanation: I don't own those games and don't play them, and I didn't have press Steam or Origin codes readily available), so I'll see about adding those to the mix before I drop the iMac back off at FedEx.

I'll also happily take suggestions for additional things you guys would like to see done to the box! Chime in below in the comments, and I'll see what I can do.

Listing image by Lee Hutchinson