PowerColor HD3870X2

Josh Collins clones himself to take on this double-threat of a graphics machine.

Two is better than one, right? Well this is the mentality AMD/ATI has progressed toward with its HD38xx series and in doing so, it imaginatively named the new flagship graphics processor the HD3870X2.

The HD3870X2 is effectively two HD3870 graphics processing units slapped side by side on a single PCB. Doing so means a number of core differences between the HD3870 and HD3870X2, both physically and technically, while also maintaining similarities considering the shared heritage of the two.

The new card consists of two R680 GPU cores with a total of 1024MB of onboard dedicated memory – each core receiving an isolated 512MB of memory to go about their business; just as if each was a separate GPU all together. Maintaining the ‘two of the same old core’ concept, each core sports 320 unified shaders and a 55nm manufacturing process. Where the card differs to its single GPU core brethren is in the physical stakes. The HD3870X2 is noticeably longer, measuring in at 26.7cm while also utilising an additional 8-pin PCIe power connection to assure the extra GPU gets the juice needed to run.

The single PCB-dual GPU solution has an integrated CrossFire bridging chip to allow the two GPU cores to communicate and act as if they were two separate entities communicating over a conventional CrossFire configuration. This has also been an area of concern for those into competitive benchmarking, or simply into their tech. It brings up a whole mountain of arguments as to whether the card is classified as a single GPU or a multi-GPU solution – we’ll leave this one to you, constant reader, to decide.

While the concept of dual GPUs on a single PCB is not anything new – check out the X1950Pro Dual from Sapphire for the last attempt – what is new in this case is the fact that the thing actually works. Not only does it work, it is not restricted to a single chipset like its forefather. To make sure this was true we tested this GPU on our NVIDIA 680i SLI motherboard test bench. We’re pleased to report that the performance as well as the overclocking capability was as would be expected on any other chipset – predominantly dominated by native CrossFire multi-GPU support.

For our testing, a 65nm Intel Core 2 Duo processor was set to a 400MHz FSB and combined with a 9x multiplier to give an end processing frequency of 3.6GHz. Paired with this was a Corsair Dominator PC2-10000 C5 2GB memory kit at DDR2-1000 with latency timings of 4-4-4-10-4-20 2T. To assure we could take advantage of the GPU crippling capability of Crysis we formatted the system with Windows Vista Ultimate 32-bit.

With the kit configured and the card running stock frequencies of 825MHz core and 900MHz memory (1800MHz effective) per each core, we set it on its merry benchmarking way to plow through 3DMark06 and Crysis. And plow it did, raking in an impressive 15,342 3DMarks – approximately 5k more than a single HD3870 on the same test bench configuration. Performance was also strong in Crysis, providing an average FPS of 17.02 and a maximum of 30.72 frames, but, oddly and much to our surprise, the minimum FPS dropped as low as 3.40 frames – we can only suggest this would be due to the dual GPU setup and a possible buffer problem. Hopefully we can see this odd minimum FPS result brought into line with further driver development.

Overclocking the card was an interesting affair. We had to treat the card as if it was a set of two single GPU cards in a CrossFire configuration. None the less, this particular sample managed 904.5MHz on both cores and 999MHz for both sets of 512MB memory with a step higher on each crystal-set resulting in artifacting. We knew from playing around with this card with the Team.AU crew that this was simply the card asking for more volts. For those adventurous in the ways of volt modding, these cards can return some very sizeable results when given the additional volts they yearn for – just be sure to have sufficient cooling!

With the overclocked frequencies set, the card saw a measly gain in 3DMark06, only scoring an extra 18 3DMarks, suggesting CPU limitations. It did excel in Crysis, however, with the average, maximum and minimum being bumped to 22.02, 32.46 and 5.94 FPS respectively.

This is an interesting concept, finally coming of age since its initial and rather ugly inception in the form of the X1950 Pro Dual; we welcome this newcomer and look forward to getting our hands on the CrossFire drivers, currently in development, that will allow for two HD3870X2 cards, with a total of four GPU cores, to communicate.