R680: AMD ATI Radeon HD 3870 X2

ATI Radeon HD 3870 X2 reference card

Core clock: 825MHz
Memory clock: 1.80GHz (effective)

When AMD launched the Radeon HD 3800 series, it said that it would drop the model name suffixes and while that is true to some extent, it makes a return with the Radeon HD 3870 X2. But that’s for a good reason though because, although AMD has referred to the ASIC as R680 in the past, the Radeon HD 3870 X2 is actually a pair of RV670 chips and a CrossFire bridge chip on one PCB.

At just over 265mm in length, the Radeon HD 3870 X2 card is roughly the same length as the GeForce 8800 GTX and GeForce 8800 Ultra – this makes it deeper than a typical ATX motherboard. Despite this though, the Radeon HD 3870 X2 fits into a standard PCI-Express x16 slot – you’ll just need to make sure that there is nothing in the way that will interfere with the card once it’s installed.

It’s good then that motherboard manufacturers have been designing their boards with long graphics cards in mind for some time now, which means that you shouldn’t encounter any clearance problems when installing this card. Obviously, the motherboard isn’t the only thing to consider when you’re wondering if this card will fit into your system – you’ll also need a case that has enough room to accommodate a card this long.


The cooler is a dual-slot solution that’s similar in design to the coolers we’ve seen recently on the Radeon HD 3870 and Radeon HD 2900 XT. Speaking subjectively, the Radeon HD 3870 X2’s cooler is about as loud as the standard Radeon HD 3870 fan which, by our reckoning, was pretty quiet. One thing’s for sure – it is much quieter than the Radeon HD 2900 XT’s cooler, as that suffered from regular changes in pitch when the GPU was under heavy load.

Some of the blame (but definitely not all of it) could be placed on the high current leakage and power consumption of the R600 GPU because, when you combine the two RV670 GPUs together, you end up with roughly the same overall power consumption. Of course, RV670 doesn’t leak anywhere near as much current, but I would say that the heatsink’s overall design—which includes the variable fan speed control—is superior.

Along the edge of the heatsink shroud, AMD has used a painted aluminium heatspreader to help cool the memory that runs along the top edge of the card. And, while we’re talking about the top edge of the card, it’s worth talking about the two power connectors.

Like the Radeon HD 2900 XT, the card only requires two six-pin PCI-Express power connectors in order to function normally, but if you’re wanting to overclock, AMD recommends one eight-pin and one six-pin connector to ensure that there is enough power available. What’s disappointing about the connectors on the reference card is that the sockets are actually perpendicular to the PCB.


This means that, if your PSU is above your graphics card in your chassis, you will have to route the cables down and then around the card before plugging them in. Thankfully, it looks like at least one board partner has changed this, because Asus has turned the connectors round so that the sockets are parallel to the PCB, making them much easier to plug in.

On the reverse side of the card, there is another aluminium heatspreader – this cools the memory on the back side of the card, while also leaving room for the two spring-loaded braces that help to ensure that the heatsink makes a good contact with the GPU.

Moving onto the PCI bracket, there are two dual-link DVI ports that both feature the two HDCP crypto-ROMs (a total of four keys) required to play protected Blu-ray and HD DVD movies at resolutions up to 2560x1600, providing your monitor can do the same as well. There is also a video out connector that sits in between the two DVI ports – interestingly, this time it’s not the VIVO port that we’re normally used to on ATI’s recent graphics cards. I guess that’s because there’s a limited amount of space on the PCB... speaking of which, let’s roll onto the next page.