ATI Radeon HD 5870 review

It’s been a while since anything truly exciting happened in the world of PC graphics cards, but the Radeon HD 5870 changes all that.

This 280mm long beast packs an incredible punch, and takes the title of world’s fastest graphics card from Nvidia’s dual-GPU GeForce GTX 295 with ease.

ATI’s goal was to make the 5870 twice as fast as the HD 4870 and, broadly speaking, it has succeeded. The older model was almost exactly half as fast as the newcomer in Crysis, producing 27.5fps. The 5870’s result of 56.4fps is nothing short of astounding, and resoundingly beats Nvidia’s GTX 295 (which managed only 44fps) and it’s also much quicker than ATI’s dual-GPU 4870X2, which posted 41fps.

The main reason why the 5870 is so fast is because the processor has 2.15 billion transistors inside it, compared with 956 million in the HD 4870. This means it has 1,600 stream processors, compared to the older card’s 800. Plus, the newcomer has a core clock speed 100MHz faster than the 4870’s 750MHz. Finally, it has 1GB of GDDR5 memory running at 1.2GHz, 450MHz quicker than the 4870’s RAM.

It’s important to note that the 5870 fully supports DirectX 11, which is part of Windows 7, and will be offered to Vista users in a future update. As it’s not exclusive to Windows 7, games developers should sit up and take more notice, and DirectX 11 games – in theory – will appear thick and fast. Currently, however, there are only a handful of DirectX 11 titles due out before the end of the year, including Colin McRae: Dirt 2, Aliens vs Predator, BattleForge and S.T.A.L.K.E.R.: Call of Pripyat.

DirectX 11 benefits

DirectX 11 is an evolution of DirectX 10, and while it still lacks some of the features that games developers have been asking Microsoft for since the launch of Vista, it does have some highlights that are sure to bring big improvements to game effects.

One is tessellation. This has been around since 2001, but with the power of new graphics cards such as the HD 5870, it can be put to use making objects and scenery in games look ever more lifelike. It increases the complexity of an object as the player moves closer to it, adding extra triangles only when they’re needed. Previously, developers had to make several different versions of an object and show the appropriate one depending on its distance to the player. Tessellation, therefore, makes the programmer’s life easier, and is why they are more likely to produce games that take advantage of DirectX 11.

DirectCompute is also new. Its main purpose isn’t for gaming, but to allow the GPU to be used for other functions. GPUs are excellent at executing instructions in parallel, while CPUs excel at executing instructions in a serial fashion. Essentially, it means that applications that can take advantage of parallel processors can run much faster. Video transcoding is a good example. Often, you’ll need to convert a video to a different format, perhaps to watch it on a portable media player. This conversion can take a long time using a CPU, but a GPU can complete the job in a fraction of the time.

A third benefit of DirectX 11 is multithreaded rendering. This simply means that the full power of a dual-, triple- or quad-core CPU can be used, avoiding the traditional bottleneck that slowed down a fast graphics card. In theory, it should lead to more frames per second in the latest games.

Power use

The good news is that the 5870 doesn’t generate twice the heat or use twice the power of the 4870. This is because ATI has used a smaller manufacturing process that reduces the GPU’s size. While the 4870 used a maximum of 160W, the new card uses little more at 188W. It uses just 27W when idle, compared to the 4870’s 90W. During our testing, the card’s fan was never noisy. While we haven’t had enough time to fully test its overclocking potential, games remained stable even when we overclocked the core and memory by 100MHz (400MHz effective for the memory).