External Graphics Performance: Gaming
We saved the best for last. What got us excited back at CES was Thunderbolt's ability to enable external graphics on a device that simply doesn't have the physical dimensions, the thermal headroom, or a big enough power supply to accommodate a modern desktop GPU (or even a mid-range desktop GPU renamed by AMD or Nvidia to sound like a more mighty performer).
This stuff has been done before. We've seen enthusiasts use the ExpressCard standard (plus significant ingenuity) to tack add-on graphics to mobile platforms in the past. Unfortunately, ExpressCard limits you to 250 MB/s (over one PCI Express 1.0 lane). Thunderbolt gives you up to eight times as much throughput, letting more mid-range graphics cards stretch their legs.
A cursory run through 3DMark 11 using the Extreme quality preset demonstrates what we saw from the OpenCL-based benchmarks. Mainly, while there is a performance hit attributable to Thunderbolt's narrower bus, it's most quantifiable using high-end graphics cards. Dipping back to the GeForce GTX 460 reveals very little difference at all.
There's a more pronounced difference at the Performance preset, probably because we're less constrained by the performance of each GPU, meaning more data is moving between the host and not-fully-taxed graphics cards.
Nevertheless, if you're looking at the difference between integrated graphics in an Ultrabook or a slightly-degraded GeForce GTX 460 on the same machine, the minor performance loss is pretty inconsequential.
Firing up real-world gaming tests is even more telling. Intel's HD Graphics 3000 engine is simply incapable of powering through a title like Battlefield 3 at 1920x1080 using Ultra quality presets. Neither AMD's Radeon HD 6970 nor Nvidia's GeForce GTX 460 struggle, though.
You can clearly see that the higher-end AMD card is faster than the GeForce in a native setting. Limiting each card's interface bandwidth puts them on even footing, though. The good news? There's no reason to spend extra money on a more expensive board.
World of Warcraft is much more platform-limited. It's probable that our Core i5-2400 running at its stock frequency is the reason AMD's Radeon HD 6970 and Nvidia's GeForce GTX 460 match each others' performance in our MSI motherboard. Pull both cards out over Thunderbolt, however, and the interface's latencies and limited bandwidth give the 6970 more of an opportunity to excel. Again, though, the more important take-away is that the Echo Express Pro paves the way for great gaming performance, whereas Intel's attempt to deliver capable graphics fall flat.