Tech preview: Asus EAH3850 X3 Trinity

With the launch of Nvidia's GeForce 9800 GX2 as a rival to the ATi Radeon HD 3870 X2, dual-GPU graphics cards are en vogue right now. But Taiwanese manufacturer Asus has upped the ante, mounting three Radeon HD 3850 GPUs on a single card with a total of 1.5GB of RAM to create what it's calling the EAH3850 X3 Trinity.

The X3 isn't officially sanctioned by AMD - it's Asus' own design, and before you reach for your wallet, be warned that the company doesn't actually plan to sell Trinity-based graphics cards. The card we tested is one of only ten in the world, produced purely as proofs of concept. There are no plans to make any more.

But while the X3 may be of no great commercial consequence, it's still an interesting artefact. For one thing, it shows up how poorly graphical processing power scales with current games and drivers. A standard 512MB HD 3850 running our Crysis benchmark in high detail at 1,280 x 1,024 averaged 26fps, while switching to the X3 increased that score by just 3fps. By comparison, a single-GPU HD 3870 brought a very similar a frame rate of 30fps.

Crysis at 1,280 x 1,024 with High settings isn't one of our primary benchmarks, but we've quoted the score as it's one of the few tests in which we actually found an increase. Even using the latest Catalyst drivers we repeatedly witnessed framerates plummeting when the third GPU was enabled, and often even with just two; it's clear that the reliability of the X3 is all over the place. We were told that older games such as Half Life 2 see far more consistent improvements, but the idea of using such a high-end card on anything but the latest games is a little ludicrous.

In case you're wondering, Asus opted for the HD 3850 GPU rather than the faster HD 3870 for reasons of power. Even with this lesser chip, our X3 test rig peaked at a whopping 296W, compared with 186W for a standard 3850 system. With an HD 3870 X2, the system exceeded 300W, and that's with just two GPUs.

Interestingly, despite this serious power draw, Asus has chosen to run the X3 from a single 8-pin connector. As it's an engineering sample rather than a real product, Asus hasn't laid down any PSU recommendations, but we played safe by giving it a powerful rail all to itself.

Another consideration is heat. Rather than trying to cram three GPUs in a row onto the card, Asus has spaced them out, placing one on the top of the card and two on the underside. This creates its own problem, though: attaching heatsinks and fans to both sides of the card would prevent it from fitting into some case arrangements, and defeat access to neighbouring expansion slots.

So instead, Asus has used a low-profile heat-pipe system that channels the heat to a heatsink at the back of the card, from where it's dissipated by externally-powered fluid cooling pipes. If the X3 were destined to be a retail product then Asus would doubtless work on a more elegant solution, but this conspicuous cooling system is a worthy reminder of the huge amount of power that's being wasted as heat for the sake of a few extra frames a second. And that's to say nothing of the power expended in dissipating that heat. Green computing it's not.

The X3 is an interesting demonstration of engineering potential, but its real value is as a demonstration of how fundamentally inefficient multi-GPU gaming is. As multi-threaded computing becomes more common, we can hope that developers focus on making 3D graphics scale better across multiple GPUs: then, at least, the extra power requirements may translate to a worthwhile performance boost. For now, though, ethical consumers should be thanking Asus for not putting the X3 Trinity into commercial production.