When it comes to graphics cards, AMD’s business strategy is difficult to beat. Its consumer-friendly mantra can be summed up thusly: more power for less money. Pretty hard to argue with, isn’t it? In terms of performance-to-cost ratio, its latest generation of graphics processing units has blown NVIDIA out of the water. Even steadfast GeForce aficionados can’t help but take note. All of a sudden the playing field is even again, with the odds arguably tipped in AMD’s favour… And now, into the breach steps the Radeon HD 4870 x2 — the fastest graphics card ever built.

After being bowled over by the ATI Radeon HD 4850 and ATI Radeon HD 4870, we were expecting big things from ATI’s HD 4870 x2. Effectively two HD 4870s crammed onto one board, it offers 2.4 teraFLOPS of graphics horse power, 1600 stream processors, 2 billion transistors and a whopping 2GB of GDDR5 memory. On paper, this makes it the fastest graphics card on the market by a country mile. However, those expecting double the performance will be in for a disappointment. Like last generation’s Radeon HD3870 X2, it basically provides a Crossfire-style configuration via a PCI express bridge. Consequently, while the speed boost is significant we wouldn’t exactly class it as phenomenal. (Further down the page we’ll compare its benchmark results to a standard HD 4870 card, to give an indication of the real-world performance gains.)

We tested Sapphire’s version of the HD 4870 x2, which is identical to the ATI reference board. With an RRP of $724, it is very attractively priced when compared to its top-tier rivals. (Indeed, NVIDIA’s high-end GTX 280 retails for nearly the same price, despite being equipped with a single GPU.) While it remains out of reach for the mainstream consumer, hardcore gamers and 3-D enthusiasts will get plenty of bang for their buck.

Before we dive into the benchmarks, let’s take a look at the new card’s architecture, as well as the design of the Sapphire board itself. As mentioned, the HD 4870 x2 has been installed with two HD 4870 GPUs (graphics processing unit) on a single printed circuit board. An improved PCI-E 2.0 bridge chip allows the two GPUs to share data at a faster and more efficient rate. Its core and GPU clock speeds, meanwhile, remain unchanged at 750MHz and 900MHz, respectively, which is identical to the HD 4870 version.

In terms of size and weight, the Sapphire HD 4870 x2 is a hefty piece of kit, requiring a roomy PC chassis with plenty of additional space. To run, the board requires a 6-pin and 8-pin PCI-E power connector, both of which are located underneath the board. We found this to be rather inconvenient and fiddly. A dual-slot cooler design is used to maximise airflow, complete with copper heatsinks which protect the GPU cores. For connectivity, a pair of Dual-Link DVI ports are provided (allowing you to hook up multiple monitors) as is a video-out port with VGA/HDMI adapters.

Like the rest of our recent graphics card reviews, we tested the Sapphire HD 4870 x2 on a Vista 32-bit machine equipped with 1GB of DDR2 RAM, a 750GB Barracuda ES hard drive and a 2.66GHz Intel Core 2 Quad CPU. In 3DMark06, the card returns an overall score of 13,989. This is one of the highest results we have ever seen, trumping the standard HD 4870 by 1138 marks. Asus’ ENGTX280 TOP (HTDP/1G/A) (a factory-overclocked card based on the NVIDIA GTX 280 chipset) received a score of 12,726.

In our gaming tests, the Sapphire HD 4870 x2 performed solidly for the most part, but we can’t say we were hugely impressed — particularly when it came to the DirectX 10 system-hog Crysis. First though, let’s look at the DX9 game benchmarks.

In the game F.E.A.R., the HD 4870 x2 averaged 198 frames per second (fps) with maximum settings enabled. This was significantly faster than the ENGTX280 TOP and HD 4870, which averaged 154fps and 121fps respectively. However, in Half-Life 2 the HD 4870 x2 was beaten to the post by its NVIDIA rival, averaging 139.6fps (compared to the ENGTX280 TOP’s result of 163.19fps). Likewise, the game Lost Planet: Extreme Conditions averaged 115fps with the HD 4870 x2 card — just two frames more than the ENGTX280 TOP.

Things were slightly more impressive on the DX10 front — provided you ignore the existence of a game called Crysis. In Call of Juarez, the Sapphire card averaged a ridiculously fast frame-rate of 84.9fps; the ENGTX280 TOP averaged 50.9fps, and the HD 4870 managed 54.3fps. In both cases, that’s a difference of more than 20fps. Things were markedly less rosy however, when we fired up Crysis…

Despite being nearly a year old, Crysis is still considered the Holy Grail of graphics benchmarks. With more than a million lines of code, 1GB of texture data and 85,000 shaders, its fearsomely complex game engine is notorious for slowing down well-equipped machines. Tellingly, AMD has neglected to include Crysis in its own benchmark statistics, preferring to stick to less power-hungry fare, like Prey and Half-Life 2. When we attempted to run Crysis ourselves, the benchmark demo crashed midway through its run. We searched AMD’s website for some HD 4870 x2-specific drivers to rectify this problem, but turned up empty-handed.

Despite the mixed benchmark tests, we still feel that this graphics card offers an appropriately high-end performance that won't let the average enthusiast down. Still, we have to admit that we were expecting a little bit more. Cautiously recommended.