The former founder of Sunnyvale, which bought it several years ago the Canadian ATI gives launched hostilities with the launch of the first DirectX 11 GPU. A month before the release of Windows 7, the new operating system from Microsoft, AMD is therefore the first graphics cards DirectX 11 compatible.
Unlike DirectX 10, DirectX 11 is certainly built into Windows 7, but it will be available separately for download for Windows Vista. This precision made, we can return to the Radeon HD 5800 launched today by AMD, so ahead of its competitor NVIDIA ... always.
For the launch, AMD offers a range consists of the Radeon HD 5850 and Radeon HD 5870, two graphics cards upscale. This last model that will occupy us in the pages that follow. After a Radeon HD 4870 already distinguished fast and also support DirectX 11, what should we expect the performance of the Radeon HD 5870? What is changing its architecture? What about consumption? So many issues we address in this test of the Radeon HD 5870.
Before proceeding to a detailed review of the architectural changes proposed by the Radeon HD 5870, we must naturally return to DirectX 11. For memory is the DirectX API, so the software library, developed by Microsoft and allows programmers to video games to access different functions of the graphics chip. Thanks to DirectX, all graphics cards speak the same language, and developer of video games has more to worry about the specifics of each.
In the past, each new version of DirectX introduced the major features that are generally reflected by a level of realism significantly higher than a generation gaming to the next. However, since DirectX 9.0, it must be noted that realism has not increased dramatically while the number of shares operator DirectX 10 is reduced .... There are thirty of DirectX 10 games have emerged since 2006 ... The fault that Microsoft chose to reserve its DirectX only operating system Windows Vista, a largely ignored by players. With DirectX 11, we said in the introduction, Microsoft did not repeat his mistake since the new API version is certainly built into Windows 7 by default, but will be soon available as a download additional Windows Vista (but not Windows XP). What motivated game developers to make the effort to bring their securities under DirectX 11.
While each version of DirectX was compatible with previous generations of graphics chips, Microsoft had shown disruptive with DirectX 10. In fact, DirectX 10 only runs on DirectX 10 graphics chip and all the code from previous versions of DirectX has been deleted. For compatibility reasons, Windows Vista was proposed course with DirectX 10 of course, but also DirectX 9.0. Again, Microsoft does not commit the same mistake. DirectX 11 is compatible with the graphics hardware DirectX 10.1 and DirectX 10 though of course its features will be limited
The new DirectX 11
Among the new DirectX 11 offers several improvements including the introduction of Shader Model 5.0, the new version of the programming language of the bullet. For the first time DirectX provides a greater degree of parallelism since the API is now able to take advantage of the various cores of your processor. The game programmed in DirectX, the DirectX runtime, but also the DirectX driver can now run in separate processes. Moreover, some tasks can run in parallel as loading a texture and a shader compiler while the main graphics rendering takes place in his thread.
The pipeline graphics processing DirectX has also been revised to offer two new types of shaders, but also support new data types. New shaders allow to operate for the first time tessellation. This feature present in the graphics chip for the Xbox 360 and in all graphics chips from AMD Radeon HD 2000 allows to multiply, without penalty of performance, the geometric details.
The chip is indeed capable from a simple figure to apply to each subdivision polygon recursive with more geometry, the graphics are richer, more detailed. DirectX 11 includes this feature at last ... standard: good news.
It is also found in DirectX 11, and for the first time, what Microsoft calls the DirectCompute. It is to standardize the various initiatives to exploit the graphics chip as a coprocessor with a common API. DirectCompute is somehow the answer to Microsoft OpenCL. Here things get complicated, because DirectX offers three versions of DirectCompute: DirectCompute 10 (or 4.0), DirectCompute 10.1 (or 4.1) and DirectCompute 11 (or 5.0). Naturally, DirectCompute 10 runs on DirectX 10 graphics chip, DirectCompute 10.1 on chips DirectX 10.1 while DirectCompute 11 works only on DirectX 11 chip. Depending on the version of DirectCompute, the maximum number of processes, the size of shared memory or the memory available in writing vary.
Specifically, DirectCompute should allow games taking advantage of exploiting the power of the graphics chip for rendering of shadows, calculating the effects of physical or even ray tracing. The management of artificial intelligence may also benefit from DirectCompute, while any software application can use DirectX DirectCompute to go directly to the graphics chip for certain calculations. One thinks of course applications handling video files that can take advantage of the graphics chip, either AMD or NVIDIA to accelerate the encoding operations.
Various limitations were also identified with DirectX 11, while compression formats textures enriched with new settings less aggressive and more respectful of the original texture.
The graphics engine is the name given to the group of units located between the command processor, which receives instructions from the system, and the calculation units themselves which will ultimately make all our operations on pixels before mixing to send them in fine on the screen. The graphics engine has various features including the geometric unit assembly, rasterization module or unit of tessellation. Our pixels pass through this unit and can undergo several operations before being forwarded to the unit responsible for the distribution calculations in the stream processors.
Our graphics engine provides a new tessellation unit: it is the sixth generation of the technology of ATI. It is fully programmable DirectX 11 and handsel a new algorithm to reduce artifacts. In addition, AMD has a very important change with the use of stream processors to perform the interpolations. It is therefore more a function pre-wired, but a programmable function thus providing greater flexibility with a reduced impact on performance. Following the performance of the unit geometry were improved, but ATI does little more detail on this subject.
ATI offers as a calculation engine twenty SIMD processors. Each has 16 stream processors, each stream processor is composed of five units. Overall it is therefore 1600 units of calculation are available in the latest Radeon. Compared to the Radeon HD 4000, and despite the improvements made to DirectX 11 and to increase performance, ATI has always vec5 type architecture: each stream processor can work on the five components of a vector. The units of our stream processors have been revised to accommodate new features such as accelerating melting calculations multiplications / additions, or the sum of absolute differences. Some of these changes were also enacted by DirectX 11. In total, the chip offers a computing power of 2.7 teraflops in single precision and 544 GigaFLOPS double precision. And do not forget to specify that the calculation units meet the standard IEE754-2008 for all of the methods of calculation.
The texture units are increasing in number, in fact they double puisqu'ATI offers 80 units. The ratio of texture units versus units of calculation remains the same as the Radeon HD 4000 and each unit displays a higher bandwidth while the amount of cache second level has been doubled. Similarly, the bandwidth of said cache is more important. Finally, ATI has support for DirectX 11 features related to textures with a maximum resolution of 16 000 x 16 000 while the compression modes 32 and 64 bit HDR are supported.
By the way, and since it comes to textures, we should note the new algorithm for anisotropic texture filtering. This improves the video quality by eliminating the dependence of angles and without impacting performance compared to the previous algorithms the Radeon HD 4000.
The ROP units, responsible for recent operations on pixels, also benefit from improvements to some functional, others clearly oriented performance. Specifically, the ROP can be treated at the Radeon HD 5800 twice as many pixels per clock cycle than the old Radeon HD 4800. And this is normal since the number of ROP is precisely ... doubled!
Conclusion
Key points of the new Radeon HD 5870 that AMD is proposing today? First AMD manages a bang as firm Sunnyvale NVIDIA is ahead by several months by offering the first DirectX 11 graphics chip.
After this success, what is the Radeon HD 5870? With twice as many units of computing, memory bandwidth up and new functionalities to support DirectX 11, the card on paper serious advantages. Yet in fact his performance is somewhat disappointing. Force is in effect held that if the card is always at the Radeon HD 4890 and GeForce GTX 285, it rarely fails to compete with dual-GPU cards like the Radeon HD 4870 X2 or GeForce GTX 295.
There are several possible explanations and most obvious is that current games do not seem to benefit from this additional power. But beyond that, and although AMD denies it, the memory bus of the RV870 seems cramped. Limited to 256-bit memory bus bandwidth provides 33% higher than the Radeon HD 4890 with GDDR5 chips faster. But this increase seems modest when related to the doubling of computing units. And despite various optimizations made to the architecture, with a doubling of the cache or increase their bandwidth, the chip seems seriously handicapped by the absence of a 512-bit memory bus. But I bet that ATI remains some room for growth with future updates to its drivers.
While the dimensions of the card seem disproportionate, he appreciates his silence and efforts at its power consumption. We must indeed recognize that this is the graphics card upscale consuming the least idle. Moreover, the Radeon HD 5870 is now the GPU faster. Moreover, it is particularly suitable for players who have a 30 inch screen. But power has a price: AMD announces a price of 349 euros. It's expensive, and one is tempted to advise you to wait as much as the first DirectX 11 games are not expected before three months at best. As for the Radeon HD 5850, it has not yet been released by AMD and its performance remains mysterious.
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