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Written by Nebojsa Todorovic
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Monday, 04 May 2009 |
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Page 2 of 6
As we already mentioned that Radeon HD 4770 is based on new technology but is it enough to achieve almost same performance levels as older brother remains to be seen. GPU that we found on Radeon HD 4770 has RV740 marking and is made in 40nm manufacturing process. It is packed with 826 million transistors compared to RV770 (HD 4850) and its 956 million transistors, is “just” 130 million less. How impressive this is, can be seen through realization of RV740 (HD 4770) that has 137mm2 and RV770 (HD 4850) 256mm2 which is almost double in size. New GPU has 640 stream processors and 32 texturing units, the same number as Radeon HD 4830 has, while number of ROP units is the same as for HD 4850. These are very good news since ATI’s usual practice is to lower number of ROP units to produce models in lower segment of product line-up. Thanks to these specifications HD 4770 based on RV740, on paper, looks slightly slower then Radeon HD 4850. Thanks to high frequency of 750MHz, HD 4770 has almost same texture fill rate to HD 4850, while pixel fill rate is higher. Memory bus is a segment where savings were made, because simpler PCB has significant role when it comes to price of budget models. Since HD 4770 has 128bit wide memory bus, first impression is that this is the segment “where the dog is buried”, but we must tell you that ATI decided to use GDD5 memory. Yes, graphics card from lower line-up segment uses GDDR5 memory in amount of 512MB, which effectively doubles the memory bus. By doing this ATI placed top notch technology into budget graphics card. Memory ships operate at 800MHz which is 3200MHz in case of 128bit memory bus or 1600MHz for 256bit bus. Of course new elements and new manufacturing process resulted in higher power consumption, so HD 4770 is declared at 80W, while PCI-e 2.0 can deliver only 75W, so 6-pin molex is present “just in case”. Of course, as all RV7XX GPU, even RV740 supports DirectX 10.1, OpenGL 2.1, Pixel and Vertex Shaders 4.1.
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Graphics card that we got in our test lab came directly from ATI so there was no packaging and additional accessories. Finally ATI used two-slot cooling solution so we don’t expect problems in that area. Cooler is very similar, or even maybe identical, to the one used on HD 3870 model. We know that it is irrelevant to comment on visual effects of budget graphics cards but we must point out that we liked red-black combination that was used on this model. PCB is slightly shorter compared to HD 4850 but still very complex. Cooling solution consists of four parts: aluminum base that covers memory chips and GPU, copper heat pipes, plastic cover that acts as air tunnel and one 70mm turbine fan. As expected, this cooling solution did its job perfectly and didn’t contribute to heating of chassis’ inside since heated air is transported into surroundings. Temperatures during tests didn’t exceed 70 degrees Celsius in automatic mode. During tests we also noticed that automatic mode isn’t well optimized because it looked like fan was operating in just two modes: minimum and maximum RPM. Because of this during our tests graphics card frequently changed its noise characteristics from silent to loud. This can be easily corrected in new BIOS so we expect that retail models will operate as expected. Also we tested noise levels and concluded that everything above 60% of maximum fan RPM is almost unbearable. When we set fan at 60% of maximum fan RPM, temperature newer exceeded 58 degrees Celsius. Power consumption was (almost) identical to ATI specifications: 78W.
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Graphics cards 
