TECHNOLOGY

Barely a year after launching its Radeon HD 5800, the first GPU family "Evergreen," AMD is back with a new set of graphics chip DirectX 11: "Northern Islands". But today, it is especially the "Barts", incorporating the Radeon HD 6800, we are interested.

AMD Radeon HD 6850 6870Mais the first question we must answer is: is it a revolution, or yet another evolution? Well those who dreamed of returning to AMD the drawing board will be disappointed here, there is no question that a simple update.

A goal for Barts: smaller ... but also efficient

However, it is not trivial as AMD has been working on one thing: the effectiveness of its architecture.

Thus, at the unit level, or almost nothing changes. There is always composed of 16 core groups of five treatment units, only one in charge of complex mathematical functions. The caches are identical, and the overall architecture of the chip.

The first novel, about us, is a disappointment: the fleas of the family to borrow Barts Radeon HD 5700 their total lack of treatment of double precision. For reasons of economy, this useful feature for fans of GPU computing was simply removed.



Second, and better news, we are treated to an improvement of the unit in charge of the tessellation. Indeed, with the launch of GeForce GTX 400, AMD had resumed the argument of this capacity attached to DirectX 11 and OpenGL 4.0 in the face, as its architecture was lagging behind that of its competitor in this .

More than double precision ... but better management of the tessellation

The manufacturer promises and performance doubled compared to the previous generation, especially with factors low, less than 10. For the father of the Radeon, game developers do not need more ... a way to explain that the results are still lagging behind NVIDIA face? No doubt. Remains to be seen that the performance will be noted in upcoming titles.

AMD Radeon HD 6850 6870Enfin it comes to the memory controller which is still 256 bits (4x 64-bit) but the cost in terms of mm ² and transistors has been extensively revised downwards compared to that of HD 5800. It remains to be seen what will be the effect in practice, and if that does not limit the rise in frequency too.

In the end, we are entitled to two GPU whose balance has changed from the previous generation chips. Indeed, as we have already noted, the computing power of HD 5800 was often untapped in practice.

It is sometimes noted as a difference in performance with the HD 5700 which was not proportional to the difference in terms of units and frequency. AMD seems to have shared this view and largely scaled down the number of processing units, approximately 30% less, as the texture units. The ROPs, for cons, do not move and remain at number 32.

And the result is there since we end up with a chip of only 225 mm ² to 1.7 billion transistors, against 314 mm ² and 2.15 billion transistors for those of HD 5800. All this is in fact engraved in 40 nm TSMC, while the 32 nm was initially suggested by AMD, and then abandoned for cost reasons, but mainly to avoid the fiasco of the commercial launch last year.