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Unlike most graphics cards we review, the HD 6870 X2 isn’t based on a reference design. Instead, this is a custom graphics card made by a handful of manufacturers, including Club3D and PowerColor, which has two AMD Radeon HD 6870 GPUs on one board working together in CrossFire mode. We’ve tested the VTX version, which is currently around £25 cheaper than its rivals.
It’s a huge, 304mm-long card – only 2mm shorter than the enormous Radeon HD 6990. You’ll have to check if your case has enough space, as it only just fit in our enthusiast Thermaltake V9 BlacX Edition test case. The board’s two GPUs have a fan each, which make a rush at idle and thunder under load. You’ll need a hefty power supply; a 600W model is recommended, and one which can provide 150W to each PCI Express connector. The card requires two 8-pin PCI Express connectors, but if you only have six-pin plugs and you think your PSU is up to it, you can use the 6-pin to 8-pin converters in the box to power the card. When running our Crysis 2 benchmark, our test PC’s power consumption jumped to 350W in intensive scenes, compared to just 190W when fitted with a mid-range AMD Radeon HD 6770.
There’s a useful mix of video outputs on the rear of the card. Along with two DVI ports, which you can connect to VGA monitors with inexpensive adaptors, there are two Mini DisplayPort and an HDMI connector. You’ll need to use at least one of the DisplayPort outputs if you want to use AMD’s Eyefinity triple-monitor feature – we could use Eyefinity with one DVI, one HDMI and one DisplayPort monitor with the Mini DisplayPort to DisplayPort adaptor in the box. If you don’t have a DisplayPort monitor and still want to game on three monitors, you’ll need to buy an active DisplayPort to DVI adaptor, which are around £17 from Amazon.co.uk.
Unfortunately, we had a lot of trouble getting the card to work properly. The driver installed fine and we enabled CrossFire mode, but our games tests wouldn’t work. In our standard graphics card test PC, which has an Intel Core i7-2600K processor and an Intel DP67BG motherboard, our Crysis 2 test would show a BSOD half-way through, and Dirt 3 showed extensive graphical corruption. We built a new PC with a Sapphire Z68 Pure Platinum motherboard and an Intel Core i5-2500K processor, and had trouble even getting to the Windows desktop, as the PC kept resetting. Changing the power supply made no difference, and the motherboards didn’t have a problem with CrossFire; two HD 6970 cards worked perfectly together in CrossFire mode.
However, when we plugged the HD 6870 X2 into a PC with an AMD Llano A8-3850 processor and a Gigabyte GA-A75M-GH motherboard, it ran perfectly. It also worked fine in an Asrock A75 Pro4 motherboard with an AMD A8-3850 and a different power supply, as well as in an Asus Crosshair V Formula motherboard with an AMD Bulldozer FX-8150 processor. It seems the card has a real problem with either Intel Sandy Bridge processors or their compatible chipsets, but is fine with AMD’s current mid-range and high-end lineup.
Once we got it working, we found the HD 6870 X2 to be a seriously powerful card. It destroyed our Dirt 3 benchmark, which we run at 1,920×1080, Ultra detail and 4x anti-aliasing, with a huge 95.4fps. When playing Dirt 3 with three monitors in Eyefinity mode at 5,760×1,080 we still saw 40fps average, and the frame rate never dipped below 30.6fps. In the more challenging Crysis 2 benchmark, again at 1,920×1,080 and Ultra detail, the HD 6870 X2 managed a smooth 45.7fps.
Considering the card is only £23 more than its nearest competitor, AMD’s Radeon HD 6970, these are impressive figures. The HD 6970 is a powerful card, but can only manage 31.1fps average in our Dirt 3 Eyefinity test, dropping to a slightly jerky 26.1fps in certain sections. The HD 6970 could also only manage 28.5fps in Crysis 2, showing you’ll need to turn down some detail levels to guarantee a smooth frame rate at all times.
In fact, the only card we’ve seen faster than the HD 6870 X2 is the Radeon HD 6990, which is an eye-watering £580. VTX’s Radeon HD 6870 X2 is a seriously fast card which is very good value, but its incompatibility problems mean we can only recommend it for use with AMD motherboards and processors. Also, if you have two spare PCI Express x16 slots on your motherboard and a power supply with four 6-pin PCI Express power plugs, you may prefer to buy two separate Radeon HD 6870 cards and run them in CrossFire mode, which will save you around £40.
