Radeon HD 4890: Technical Specifications and Features
So what are the new ATI graphics cards actually like? Let’s take a closer look at their technical specifications:
At first glance Radeon HD 4890 only differs from the predecessor, Radeon HD 4870, by the GPU and memory clock frequencies. However, if you take a closer look at the technical specifications above, you will see that RV790 has a few features distinguishing it well from the RV770 core. At least, it has 3 million more transistors and hence a 22sq.mm larger die. So what have they done?
Nvidia is not the only one who knows that the best is the enemy of the good. Successful graphics architecture hasn’t been changed since RV770. However, Advanced Micro Devices developers and engineers put a lot of efforts into making RV790 work stably at 850MHz frequency. They also did their best to lower the power consumption of the new GPU at least in idle mode.
When they designed RV790, they revised the entire RV770 internal structure quite significantly, having rebalanced internal chip timings and optimized its internal power circuitry. The memory controller now supports burst read, which was earlier implemented in RV710 and 730. But most importantly, they added a capacitor Decap Ring along the entire RV790 perimeter, which should improve the signal quality by lowering the parasitic noise. As the clock frequency increases, the influence of this noise on the GPU and memory stability becomes more and more serious. All these measures called for more transistors within the new core. However, in fact, RV790 became only 0.3% more complex, which is a really small price to pay for the ability to work at 850MHz+ frequencies.
Note that it is for the first time in history of consumer 3D graphics that one of the graphics giants announced their new product in two official incarnations: regular and overclocked. It is usually the launch partners who roll out overclocked graphics card modifications, but in this case Radeon HD 4890 is really announced twice: as a Radeon HD 4890 with 850MHz core and as a Radeon HD 4890 OC with the core clock starting at 900MHz. The important thing is that the latter is under full official Advanced Micro Devices support. These graphics cards will most likely be manufactured with specially selected RV790 GPUs that are guaranteed to work at 900MHz+. The actual technical specs of the product will depend on the maker, so we will most likely see elite Radeon HD 4890 OC solutions that will be able to reach 1000MHz GPU and 1250 (5000MHz) MHz memory frequencies, especially since GDDR5 memory chips with these characteristics are available from Qimonda, Hynix and Samsung. It is important that both Radeon HD 4890 models will be available in mass quantities right after the official launch. The advantage here is on ATI’s side, because Nvidia is going to start selling its alternative, GeForce GTX 275, only on April 14 – almost 2 weeks after the launch.
The first batch of Radeon HD 4890 and Radeon HD 4890 OC will include only solutions using reference PCB design and cooling systems. However, in the near future we will undoubtedly see unique products based on proprietary layouts from the large graphics card makers, such as Asustek Computer or Gigabyte Technology.
The first solution on the new ATI GPU was the Radeon HD 4890 OC from Tul Corporation branded as PowerColor HD4890 Plus. We are going to use it as an example to study all peculiarities of the new product from Advanced Micro Devices launched today.