Graphics: A substantial bump

There are three new GPUs in the new iMacs: the AMD Radeon 6750M, 6770M, and 6970M. Unlike their desktop counterparts, the 6750M and 6770M are true 6000-series GPUs, and not just rebadges of the 5750 and 5770 (though, as always, making direct comparisons between desktop and mobile parts remains difficult).

On the entry-level iMac, the 256MB Mobility Radeon HD 4670 has been replaced by a 512MB Radeon HD 6750M – you get double the graphics memory, a switch from GDDR3 to GDDR5, DirectX 11, OpenGL 4.1, and OpenCL 1.1, as well as Eyefinity+ and UVD3 and the other Radeon 6000-series niceties. For gamers, this should substantially improve performance, especially if you’re interested in trying to game at the 21.5” iMac’s native 1920x1080 resolution.

Moving up the chain to higher-end models, the 512MB 6770M isn’t as big a step up from the previous generation’s 512MB Mobility Radeon 5670 – like the desktop cards, the 6770M is essentially a higher-clocked and gently tweaked revision of its previous-generation counterpart, and higher clocks are likewise all that separate it from the 6750M. You pick up UVD3, but a lot of the on-paper specs are the same. It’s still an improvement over the previous generation, but compared to the low end and (as we’ll see) the high end, it’s not as substantial.

And, finally, we’ve arrived at the high end 27” iMac, which gets a 1GB 6970M to replace last year’s 1GB Mobility Radeon 5750. The 5750 is more or less a midrange graphics part – the mobility 5600 and 5700 series GPUs all share the same core, codenamed Madison – but the 6970M is a true high-end part, complete with a 256-bit memory bus (compared to a 128-bit bus for the 5750) and more than double the shaders (960 in the 6970 versus 400 in the 5750). This, again, will drastically improve the new iMac’s utility as a gaming machine – the 6970M is much more capable of driving the 27” iMac’s 2560x1440 pixel display. Update: Further research has revealed that the 5750 that shipped in last year's iMac was in fact a rebadged member of the mobility 5800 series using the "Broadway" core instead of the "Madison" core used in Mobility 5600 and 5700 parts. The 5800 series has 800 shaders and not 400, so while the bump in the new 2011 iMac is still a decent one, it's not as monumental as previously reported.

For the 27” models with two Thunderbolt ports, the 6000-series GPUs will also enable the use of three displays simultaneously, which will be handy for the Final Cut and Photoshop junkies who often invest in the higher-end iMacs.


The last thing I want to talk about is the subtle factor looming over these refreshed computers: Lion.

OS X 10.7 is supposed to bring a lot of iOS features “back to the Mac” when it releases this summer, and since these Sandy Bridge Macs are going to be the first computers the new OS ships on, we’re seeing some preparation for it on the hardware end.

To drive the iOS inspired touch enabled features, each new iMac can come bundled with either the touch-enabled Magic Mouse or the Magic Trackpad at no extra cost (it’s your choice – the Magic Mouse is the default option). The vanilla Apple Mouse is still a selectable option, but will save you no money compared to its touch-enabled counterparts, which are more expensive at retail.

Apple is also beginning to push SSDs in its laptops to replicate the quick boot and shutdown times of iOS, and we’re beginning to see that in the new iMacs – while none of the computers include an SSD by default, you can configure all but the entry level to include a 256GB SSD as either the primary hard drive or a secondary drive. Characteristically, Apple hasn’t posted anything about the manufacturer of this drive or its controller – Apple uses Toshiba SSDs in the Sandy Bridge MacBook Pros, and recently switched to Samsung SSDs for the MacBook Airs, but there’s really no telling exactly what these iMacs are packing until it’s in your hands.

To replace the mechanical hard drive with a 256GB SSD costs a whopping $500 ($600 to get the SSD and keep the mechanical hard drive as well), though that’s not too far above the market price for an SSD at this capacity. Also note that, at this point, TRIM only seems to be enabled in OS X for SSDs direct from Apple – even if you can put in an SSD as an aftermarket upgrade, you may not be as satisfied with its performance. This may change in Lion, but we have no solid evidence to that effect.


With this refresh, Apple has done what Apple typically does: offer faster hardware in a similar physical package while maintaining price points across the board. Quad core processors and beefier dedicated GPUs make these better buys, relatively speaking, than last year’s models, but the iMac is still the iMac: a midrange-to-high-performance all-in-one with a high-quality display. Today’s upgrades do nothing to change the iMac lineup on a fundamental level.

That is to say, if you were in the market for an iMac already, congratulations! Today’s iMac is faster and more capable than yesterday’s iMac on all fronts. If an iMac isn’t what would best suit your purposes, though, today’s update won’t do much to change your mind unless you were looking for better gaming performance on the low and high ends.

For more about the nitty-gritty on the new iMac's performance and internals, keep an eye out for our in-depth review in the coming weeks.

Specs and CPUs
Comments Locked


View All Comments

  • Andrew.a.cunningham - Wednesday, May 4, 2011 - link

    You're right to be suspicious - it's not an Apple exclusive, but it will be awhile before other OEMs jump on the bandwagon (if they decide to). I've corrected the article.

    I also think you may be right about Thunderbolt having the potential to be another Firewire - Firewire 400/800 is, in some respects, technically superior to USB 2.0, but USB is simpler and cheaper to implement and everyone was already used to it, so it's still everywhere while Firewire ports are limited mostly to Macs, add-in cards and higher-end motherboards. Thunderbolt could be better enough than USB 3 that this doesn't happen again, but it's impossible to say at this point.
  • Zandros - Tuesday, May 3, 2011 - link

    I might be wrong, but my impression was that the GPUs in the 2010 iMacs were desktop cards, or rather mobility cards marketed with the equivalent performance desktop numbers.

  • Tamz_msc - Wednesday, May 4, 2011 - link

    They're mobile CPUs, else how could a desktop HD 5770 be made to fit inside it?Apple might have been lying with their previous spec sheets.
  • Zandros - Wednesday, May 4, 2011 - link

    Did you read the second part of my sentence?

    According to all evidence I've seen, the "5750" in the 2010 high-end iMac was in reality a mobility 5850 (i.e. a mobile card with roughly equivalent performance to the desktop 5750), when the article claims it was a mobility 5750.
  • AmdInside - Tuesday, May 3, 2011 - link

    The problem is that Thunderbolt is not backwards compatible with any technology. It will be a while before consumers adopt Thunderbolt me thinks. At least firewire had camcorders to push the technology.
  • Focher - Tuesday, May 3, 2011 - link

    Actually, that's not really true. Any PCIx based device can be switched to Thunderbolt with minimal engineering effort. DisplayPort compatible devices are obviously fine out of the box.

    At NAB this year, lots of Thunderbolt devices were demonstrated.
  • mianmian - Tuesday, May 3, 2011 - link

    For PCs, it has a big problem to use thunderbolt : the discrete graphic card.

    Since thunderbolt need to carry video signal, thunderbolt need changes to the current discrete graphic card. Before AMD and Nvidia work out the Optimus like technology for desktop, thunderbolt can hardly go to desktop PCs. Maybe we can see it goes to notebook PCs first.
  • Tros - Tuesday, May 3, 2011 - link

    I'm probably newb'ing this up, but can't video cards already do off-screen rendering, and isn't Thunderbolt a DMA interface? The video-card doesn't need to be changed at all, IMO. It's probably just the drivers that need retooling.
  • Focher - Tuesday, May 3, 2011 - link

    Thunderbolt doesn't NEED to carry a video signal. It can, but it doesn't have to. You can easily have separate discrete GPUs that never touch Thunderbolt and have no impact whatsoever on it. Or they can work together with a software driver to switch between a Thunderbolt-based display versus one running off of a discrete GPU.
  • mianmian - Tuesday, May 3, 2011 - link

    According to wiki:

    Because the PCIe bus does not carry video data, it is unclear whether a standalone PCIe card could offer a Thunderbolt port. The Intel Thunderbolt Technology Brief does not give a conclusive answer.
    Thunderbolt can be implemented on graphics cards, which have access to DisplayPort data and PCI express connectivity, or on the motherboard of new devices, such as the MacBook Pro.

    Thunderbolt without video single is unknown yet.

Log in

Don't have an account? Sign up now