Thunderbolt iMac: the perfect compromise

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Pundits have predicted the death of the desktop for years. I wish it could be so. No technology is more deserving of retirement than the sheet-metal black box and tangle of cables that is the standard PC.

Notebooks and tablets have undeniable appeal: There's only one item to buy, no pieces to plug together. They're silent and power-efficient. They emerge from the box ready to work. But portable devices have limitations that can make them inconvenient if portability isn't your primary consideration. Their displays are too small. The need to run on batteries, and the cramped confines of a compact chassis put a tight limit on memory, storage, and performance. When you reposition the display, the keyboard and pointing device (real or virtual) move, too. Making computers portable also makes them expensive. As long as portables have these strikes against them, the desktop will live on.

[ Also on InfoWorld: "Thunderbolt MacBook Pro: The last notebook you'll ever need" | Subscribe to InfoWorld's Technology: Apple newsletter. ]

Apple thinks it's possible to have it both ways, to cross the convenience and efficiency of a portable with the performance and ergonomics of a desktop. Like other manufacturers, Apple has long toyed with this formula with varying degrees of success. The latest generation of iMac, Apple's all-in-one desktop computer, gets it completely right.

Occupying the equivalent desk space of an LCD monitor and requiring only one cable (power), iMac is a fast, capable desktop with a very un-Mac-like price tag. Apple's redesign equips all iMac models with second-generation Intel Core i5 quad-core desktop CPUs, faster RAM, gamer-grade AMD Radeon HD 6000M-series discrete graphics, Thunderbolt I/O, a Bluetooth keyboard and pointing device, a FaceTime HD camera, and marvelous speakers. A 21.5-inch (visible), LED-backlit HD display graces Apple's two value-priced models, while buyers of the 27-inch iMac are treated to a much higher-resolution display (2,560 by 1,440), a faster CPU, an upgraded GPU, room for up to 16GB of RAM, and a pair of Thunderbolt ports.

Traditionally, Apple has aimed iMac at consumers, steering commercial and professional buyers toward the much faster, more expandable Mac Pro. The iMac is still priced like a home computer, but for the first time, iMac's performance is as prominent as its design, in league with top-shelf single-processor desktops. If Apple's best stock configuration still isn't fast enough for you, you can upgrade to a Core i7 CPU and an AMD Radeon HD 6970M GPU with 2GB of GDDR5 video memory, enough to satisfy a power user.

The 27-inch iMac can actually accommodate two external dual-link DVI displays, each with a resolution of up to 2,560 by 1,600, creating a three-headed dream machine that still has room to connect to the next generation of ultrafast Thunderbolt peripherals. This isn't just new territory for the iMac, but for all desktop PCs outside the workstation class.

Thunderbolt iMac: Surprising performance The new iMac lineup features quad-core Intel second-generation Core i5 ("Sandy Bridge") desktop CPUs and AMD Radeon HD 6000M-series discrete GPUs across the board. The fact that all models share 6MB of L3 cache, 1,333MHz DDR3 RAM, and 7,200-rpm hard drives narrows the performance gap between iMac models enough that most buyers can simply shop for the display size that suits them.

iMac upgraders, as well as users of PCs with first-generation Core CPUs, will definitely feel the kick. Sandy Bridge's on-chip memory controller, roomy cache, and faster RAM contribute to Apple's claimed 1.7X performance boost over prior-generation iMacs, and that technology is common to all configurations. Even the bargain hunters get a ride on the bullet train.

Apple realizes that for some, fast isn't fast enough. A Core i7 CPU upgrade is available as an affordable configure-to-order option for both 21.5- and 27-inch models, bumping top clock speeds to 2.8GHz and 3.4GHz, respectively. Developers, creative pros, sci-tech workers, people who run Windows in virtualization, and others who routinely max out their multicore CPUs but lack the budget for a Mac Pro finally have a machine of their own. The iMac's Core i7 upgrades not only kick up the clock speed, but also expand L3 cache and add Hyper-Threading, likely adding a 20 to 30 percent speed bonus over Core i5. That's a meaty upgrade for $200.

The AMD Radeon HD 6000M-series GPUs that Apple chose for iMac are uncommonly powerful for mainstream desktops, rendering iMac's lack of internal expansion slots into a non-issue for most buyers. The 21.5-inch iMac incorporates either the AMD Radeon HD 6750M or 6770M with 512MB of dedicated GDDR5 video memory. The entry-level 27-inch iMac also has a Radeon HD 6770M with 512MB of VRAM, while the top-end 27-inch model (the model I reviewed) has a Radeon HD 6970M with 1GB of VRAM (upgradable to 2GB).

These GPUs don't transform iMac into a workstation (to keep a lid on cost, space, power, and heat, iMac uses mobile GPUs) but Apple has selected the market's best. These AMD mobile GPUs compare favorably with AMD Radeon HD 5000-series desktop graphics cards, which continue to be sought after by PC gamers. If you're currently an iMac user, Apple says you should expect as much as a threefold hike in graphics performance. If you're coming to iMac from Mac Mini, MacBook, or a mainstream PC that uses integrated graphics, iMac's GPU will take your breath away.

Mac OS X's frameworks and popular Mac apps deftly distribute the compute workload across CPU cores, threading engines (in the case of Core i7), and GPU shaders. Users will find that Apple's combination of leading-edge technologies from Intel and AMD add up to a smooth, exquisitely responsive driving experience. As nice as it is under Snow Leopard, it's almost sinful under OS X Lion.

Thunderbolt iMac: Benchmark results If you're considering pressing a notebook into desktop service, iMac's superior performance should factor into your decision. Benchmarks comparing a 3.1GHz 27-inch Core i5 iMac to a 2.2GHz Core i7 17-inch MacBook Pro show iMac to be the clear performance champ, and the thread-intensive SPECjbb2005 benchmark doesn't even highlight the benefits of iMac's desktop-speed hard drive. Although it's possible to configure high-end portables like MacBook Pro with a 7,200-rpm hard drive and an upgraded CPU, you'll spend a lot to construct a notebook that's in iMac's league.

I don't have a current Mac Pro for testing, but benchmarks run against an older eight-core Nehalem Mac Pro reveal iMac's generational advantage. The iMac scales remarkably well to SPECjbb2005's multithreaded workloads, even when pushed to run eight threads without the benefit of Hyper-Threading. The iMac has the headroom to handle a demanding mix of foreground and background tasks without bogging down the user interface. (See the table of SPECjbb2005 results.)

Notes: Thunderbolt iMac configured with 3.1GHz quad-core Core i5 CPU, 6MB L3 cache, 4GB of 1,333MHz DDR3 RAM; Thunderbolt MacBook Pro configured with 2.2GHz quad-core Core i7 CPU, 6MB L3 cache, 4GB of 1,333MHz DDR3 RAM; Core 2 Duo MacBook Pro configured with 2.8GHz dual-core Core 2 Duo CPU, 6MB L3 cache, 4GB of 1,067MHz DDR3 RAM; Nehalem Mac Pro configured with two 2.93GHz quad-core Intel Xeon CPUs, 8MB L3 cache, 12GB of 1,066MHz DDR3 RAM.

The iMac's CPU is capable of some impressive feats on its own, but it's Apple's ingenious pairing of top-shelf tech from rivals Intel and AMD that makes iMac tick. Mac OS X's OpenGL-based GUI suits any Mac, but it's clearly designed to run on a modern discrete GPU. AMD's Radeon HD 6000M-series GPUs are a Goldilocks fit for iMac: They have enough juice to smooth OS X's scrolling and transitional animations and deliver satisfying frame rates on 3D games, while avoiding the overkill in heat, power, noise, and cost that a Radeon HD 6000-series desktop GPU would bring to the design. Apple's decision to go with mobile GPUs may elicit a lukewarm response from hard-core gamers, but that's not iMac's niche. The iMac's architecture is optimized for Mac OS X, and vice versa.

Notes: Thunderbolt iMac configured with AMD Radeon HD 6970M discrete GPU; Thunderbolt MacBook Pro configured with AMD Radeon HD 6750M discrete GPU, Intel HD 3000 integrated GPU; Core 2 Duo MacBook Pro configured with Nvidia GeForce 9600M GT discrete GPU, Nvidia GeForce 9400M integrated GPU; Nehalem Mac Pro configured with AMD Radeon HD 4870 discrete GPU. Core 2 Duo MacBook Pro results are not directly comparable to Intel and AMD GPUs because a different shape is used, but do reflect relative performance.

Thunderbolt iMac: The human factor Desktop manufacturers tend to give short shrift to the human interface essentials: the display, keyboard, and pointing device. PC makers' catalogs are stuffed with upscale peripherals, highlighting the fact that what they bundle with their systems is almost uniformly junk. When comparison shopping, you have to disregard a PC's lowball total system price. Consider instead the true cost of the whole system after you swap out the bits that you see and touch for devices that you actually want to use.

That caveat doesn't apply to iMac. The LED-backlit displays are bright and sharp with accurate color rendition and good dynamic range. The screen on the 27-inch iMac is dreamy, and the plentiful extra pixels give you room to spread out without resorting to a second monitor. The iMac's glossy glass face lets all the light through instead of scattering it the way matte surfaces do, raising the apparent sharpness and deepening blacks.

The iMac's chassis is strictly desktop -- there are no holes for a VESA wall or articulating arm mount. The chassis is balanced on an elegant, one-piece aluminum easel that lets you tilt or rotate the display with one hand. Instead of using sticky rubber feet, the easel has a skid pad that lets you move the iMac easily, but not too easily, around your desk. There is no height adjustment, but the tilt angle range is broad enough to give you a straight-line view from anywhere. And for those times when you need to move the iMac to another room, say, to give a presentation, it's readily luggable, and its one-wire design makes relocation a snap.

If you do need another display (or two, if you have a 27-inch iMac), you can plug a mini DisplayPort to DVI or HDMI adapter into the Thunderbolt port. For resolutions beyond 1080p, make sure you buy a dual-link DVI adapter. When you're planning your iMac system, you can think of the built-in display as your primary or secondary monitor. Your monitor preference kicks in after OS X finishes booting.

When you go online to buy your iMac, you're offered a couple of simple but important choices. The standard keyboard and pointing device are Bluetooth-based and first-rate. The keyboard is a compact layout (the keys are full size) that's familiar to Apple notebook users. If you prefer a full keyboard with a numeric keypad and function keys up to F19, it won't cost you any money, but it will connect via USB. You can't lose either way; Apple's keyboards have the sweetest feel. If you're a keyboard connoisseur, go ahead and sample aftermarket alternatives. You'll come back to Apple.

As with the keyboard, Apple lets you choose between two pointing devices. Here, I implore you to set aside any presumed preference for a mouse, which is what you get by default, in favor of Apple's Magic Trackpad. The touch-sensitive top of the Magic Mouse provides only a small subset of OS X's multitouch experience. While you can get around just fine in Snow Leopard with a mouse, Lion is all about touch.

Once you drop your prejudice and make the switch, you'll discover that Magic Trackpad is brilliantly engineered. It's much larger than a notebook trackpad, yet takes up less desk space than a mousepad. Your fingertips glide across the smooth glass surface, making multitouch gestures -- and noiseless left and right clicks without buttons -- feel natural. Once you try it, you'll be hooked. Magic Trackpad is the only way to drive any Mac.

I'm not much of a Webcam user, but those who are will find FaceTime HD to be a substantial step up from the VGA-format camera in prior iMacs. The wide aspect lets multiple users participate in the video call or podcast without squishing their heads together. For those videos you can shoot in front of your iMac, there's no need for a tripod and a camcorder. A sensitive microphone is built into the chassis, or you can use the mic on either an iPhone-compatible wired headset or a Bluetooth headset.

The iMac's built-in, bottom-firing speakers are marvelous. Once again, very few iMac buyers will find it necessary to spend money on external speakers. If you want to plug the iMac into an amplifier or other sound system, you can feed the system's optical digital output straight into any component that accepts Toslink input. You can also plug an HDMI adapter into the Thunderbolt port for combined video and audio.

As for aftermarket expansion, only the RAM sockets are user-accessible. The 21.5-inch model has two sockets for 1,333MHz DDR3 SO-DIMM modules, while the 27-inch iMac has four. Beyond that, it's best to consider the iMac's chassis sealed. Make sure you configure iMac with the SATA hard disk and SSD options you prefer at purchase time. To add storage you'll have to resort to USB or NAS, or wait a few months for Thunderbolt peripherals to appear. When Thunderbolt does show, if it lives up to specs, external storage will perform as well as, if not better than, internal drives.

For the majority of desktop users, iMac renders the black-box PC obsolete. Prior objections to iMac on performance grounds have been answered by Apple's engineers, who have created a machine that's not only convenient and loaded with extras, but easily rivals the performance of any single-processor, component-based desktop system you could build with a similar budget. Apple's re-engineered iMac could become a desktop staple among professionals and consumers alike.

This article, "Thunderbolt iMac: The perfect compromise," was originally published at InfoWorld.com. Follow the latest developments in computer hardware and mobile technology at InfoWorld.com. For the latest business technology news, follow InfoWorld.com on Twitter.

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