The Gaming Capabilities of the New iMacs' GPUs

By Wesley Fenlon

Apple's latest iMacs trade out Nvidia GPUs for AMD mobile processors, which promise better (but not great) gaming performance.

Apple’s iMac refresh from Tuesday follows along with a few expected upgrade trends we saw earlier in the year with the MacBook Pros: the introduction of Sandy Bridge processors, Intel Thunderbolt and a switch from Nvidia to AMD graphics processors. That annual GPU upgrade can mean only one thing: it’s time to size up the iMac’s performance and see which of today’s hottest games the new graphics cards can handle. 2011’s all-in-one Apple desktops offer three GPU tiers across its two models; the 21.5” iMac comes in 6750M and 6770M configuration, while the 27” model adds a 6970M GPU into the mix.



6750M, 6770M and 6970M GPUs.

Graphics Card 6750M 6770M 6970M
Core Speed 600 MHz 725 MHz 680 MHz
Shader Speed 600 MHz 725 MHz 680 MHz
Memory Speed 900 MHz 1600 MHz 900 MHz
Memory Type GDDR5 GDDR5 GDDR5
Memory Amount 1024 MB 1024 MB 2048 MB
Pipelines 480 480 960
DirectX Support DirectX 11 DirectX 11 DirectX 11

Now on to the good stuff: how well can these graphics cards really run games? Gamers who care about graphics aren’t going to be satisfied with the performance of the 6750M or 6770M, but the 6970M handles modern games quite capably with two gigs of DDR5 RAM. Unfortunately, trying to play anything at the larger iMac’s native 2560x1400 will see performance take a serious nosedive. But if you can live with 1920x1080, everything but Metro 2033 puts up solid framerate numbers.

The benchmarks from NotebookCheck don’t run on the exact same hardware as the new iMacs, so results will vary by processor and RAM configurations (notably, these tests were run on laptops running a mobile Core i7 from the Nehalem generation). But in general, these scores show what the mobile Radeon graphics cards can handle.

6750M

The weakest of these Radeon GPUs is best suited to running indie games, but it’s perfectly capable of handling the latest and greatest graphical powerhouses at low settings. At a resolution of 1024x768, StarCraft II and FIFA 2011can crank out more than 200 fps. At their highest settings, though, most games deliver sub-30fps performance at 1920x1080 with heavy anti-aliasing. Crysis 2 and Metro 2033 each slow to a 12fps crawl on ultra.

Bottom line: Playing games on the 6750M will require a little fiddling with graphics settings to find a satisfactory middle ground. Compromising on settings--or playing older/less demanding games--will be a necessity.

6770M

The middle Radeon obviously fares better than the 6750M thanks to higher clock speeds across the board, but NotebookCheck’s scores show that high settings are still a no-go for hardware intensive games. At a medium resolution of 1360x768, several games including StarCraft II, Colin McRae: DIRT 2 and Call of Duty: Modern Warfare are playable at near 60fps or even higher.

Bottom line: In the 21.5” iMac, the 6770 is a smart upgrade for anyone who wants the best graphics performance available. In the 27” model, the disparity between the 6770’s mid-range performance and the monitor’s 2560x1400 resolution will be further exaggerated--better step up to the 6970M.

6970M

Here is it: the best GPU available in the newly revamped iMacs. The 6970M doubles down on GDDR5 RAM and stream processors for a total of 2048MB and 960, respectively. Those numbers stand for better performance: while NotebookCheck only ran the card at 1920x1080, it was capable of cranking out a stable 30fps in Crysis 2, 60+ in Black Ops and 58fps in StarCraft II with each game performing at ultra settings. Again, those numbers will see a significant drop at native resolution--if that doesn’t sit well with you, buying an iMac for gaming probably isn’t the smartest move. Only Metro 2033 saw the framerate dip below a playable 30--on the other end of the spectrum, FIFA blazed along at 120fps.

Bottom line: Indie favorites like Torchlight and Magicka and mid-2000s games should run like a dream on the 6970M, but you’ll have to live with running modern games at below 2560x1400 to see framerates stick to a steady 60fps.