Twin-GPU graphics cards keep coming, but not always to steal the performance crown. The latest from ATI is a dual version not of the top-end HD 4870, but its slower sibling, the HD 4850.

It has two cores running at 625MHz: each offers 800 stream processors and 1GB of RAM. It’s a real monster, too, a good centimetre longer than other X2 cards we’ve seen, and several inches longer than most motherboards are wide.

The three-pin and four-pin power connectors are sensibly positioned on the side to allow you to reach them, but it will still be a squeeze in many PCs.

With 2GB of RAM on the card, we went for a 64-bit Windows installation to make sure all of our 3GB of system RAM was recognised, but problems occurred immediately.

At first Intel’s X58 chipset driver didn’t recognise the video controller, then when we’d fixed that the latest ATI driver – the same Catalyst 8.11 as supplied by Sapphire – failed to recognise the card.

The only way we could get it working was by rolling back to an earlier beta version of the same driver, which isn’t the best start.

With the card up and running, we found it inconsistent. In easy tests it ran slower than a single HD 4850, scoring 48fps in Crysis on Medium settings and 81fps in Call of Juarez.

When we pushed harder it improved, managing 44fps in Crysis at 1680 x 1050 and High settings, compared with 32fps of the single GPU card. At Very High settings and 1920 x 1200 it remained playable, averaging 29fps. In Call of Juarez at High settings it reached 30fps.

If you push it hard, you’ll see benefits. But is this worth two-and-a-half times the cost of the HD 4850, and $130 less than a HD 4870 X2? Maybe when the driver issues are sorted that answer might be yes, but not now.