Radeon HD 4850 x2

In recent years, AMD has distanced itself from the high-performance single-GPU market in favour of cheaper, share-loading solutions. Much to the chagrin of 3-D traditionalists and hardcore gamers, its latest top-of-the-range offerings have all adopted a ‘dual core’ approach, with multiple GPUs crammed onto a single graphics card.

As you can probably guess from its name, the Radeon HD 4850 x2 is the latest addition to this contentious family, following in the footsteps of the Radeon HD3870 X2 and ATI Radeon HD 4870 x2. In theory, it combines the power of two ATI Radeon HD 4850s for a significant boost in speed and performance, though we did experience some mixed results during our benchmarks. With that being said, it will still provide the required grunt for modern 3-D gaming, and it comes with some nifty onboard features, including four DVI ports.

Like the costlier Radeon HD 4870 X2, the Sapphire Radeon HD 4850 x2 features two RV770 graphics processors on a single printed circuit board. For those out of the Radeon loop, RV770 is the foundation chip in ATI’s new generation of Series 4000 GPUs. Some of the improvements it offers over the previous chipset include a substantial increase in stream processors (up from 320 to 800), UVD2 support (which provides advanced Blu-ray/high-definition functionality) and a wider 256-bit memory bus. The HD 4850 version, released in June, comes with a memory clock speed of 1986MHz (effective), a core clock speed of 625MHz and between 512MB and 1GB of GDDR3 memory (depending on the model).

With its ‘double or nothing’ approach, the HD 4850 x2 boasts twice the specifications of its single-GPU cousin — that’s 1600 stream processors, two 256-bit memory processors and a whopping 2GB of GDDR3 memory (the core and memory clock speeds remain unchanged). It essentially uses ATI's CrossFire technology to render 3-D applications, with both GPUs sharing whatever processing tasks are thrown their way. On paper at least, this translates to faster rendering times and increased frame rates in games.

In terms of design, the HD 4850 x2 is an intimidating beast of a card, with dimensions that exceed everything else on the market. This could pose a problem for people with cramped cases, especially if they plan to set up a CrossfireX configuration. Curiously, the card requires both a six pin and an eight pin PCI connector to run, which puts it in the same league as the beefier HD 4870 x2. While this provides the card with up to 225 Watts of power, it also adds to the clutter — something this plus-sized card could do without.

For cooling, the HD 4850 x2 sports a sizeable heat sink connected to a pair of smart looking fans (one for each RV770 core). When the card was under load, we found the fans were slightly louder that we’re used to, though they shouldn’t be too distracting (provided you keep your speakers' volume at a respectable level). On the plus side, we found the card to be significantly cooler than the HD 4850 and HD 4870, which both suffered from potential overheating issues. You can also manually adjust the fans' speed (and racket) via ATI’s Catalyst Control tool.

As mentioned, the HD 4850 x2 also sports four DVI ports, which is twice the number of a typical card. This is great news for any monitor fetishists our there, who can attach up to four displays to their PC using just one card. Presumably, if you elect to set up a CrossFire configuration with two HD 4850 x2s, this can be extended to a frankly ridiculous eight monitors. All of these outputs can be converted to HDMI (complete with integrated HD 7.1 Audio) via a bundled adapter.

So what about those all-important gaming benchmarks? Unfortunately, this is the one area where the HD 4850 x2 failed to wholly impress. We tested the card 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. While it performed solidly enough, we were expecting a little more oomph from such a decked-out card. The NVIDIA-based Asus ENGTX280 TOP (HTDP/1G/A) (RRP: $699) managed to trump it in the majority of our tests. This probably says something about the advantages of single-GPU configurations, but we’ll leave that discussion for another time.

When we ran 3DMark 06, the Sapphire Radeon HD 4850 x2 received a score of 11,618. While this isn’t an awful result, the ENGTX280 TOP managed to beat it by 1107 marks, which is a pretty significant margin. In our DirectX 10 Crysis demo, the Sapphire card chugged along at 18.24 frames per second. This was much slower than the GTX card, which averaged a phenomenal 37.32fps. (To be fair, Crysis has never been particularly kind to Radeon cards, which is why ATI neglects to include the game in most of its in-house benchmarks.)

In the DX10 game Call of Juarez, the HD 4850 x2 came out on top, averaging an impressive 69.9fps (compared to 50.9fps on the ENGTX280 TOP). However, the good news ended when we ran the game Lost Planet: Extreme Conditions, with the ENGTX280 TOP’s average of 97.5fps smashing the HD 4850 x2’s 72.5fps.

With an RRP of $793, the HD 4850 x2 is far from cheap. In fact, it would be more cost-effective to fit your PC with two Radeon HD 4850 cards, though this will naturally require a CrossFire-capable motherboard and also takes up more room.