While the Radeon HD 4600 acquired a special processor called RV730, the Radeon HD 4830 doesn’t have a new chip. It uses an ordinary RV770 with some subunits disabled.
This is a justifiable approach because the manufacturing cost of the RV770 is not too high, especially in comparison with Nvidia’s G200. Cores that didn’t pass the frequency check or have defects in some subunits may also be installed on the new card. As a result, the Radeon HD 4830 differs from the Radeon HD 4850 with lower frequencies and fewer ALUs and TMUs. The difference isn’t big, though. Two out of the ten (160 ALUs) available SIMD arrays and two groups of corresponding texture processors (8 TMUs) are cut off. Thus, the new card looks preferable to the GeForce 9800 GT, being inferior to it in the frequency of the execution part of the core but far superior – nearly six times as good as its opponent – in terms of ALUs.
When it comes to the TMU subsystem, the GeForce 9800 GT formally has 56 texture processors, but they are only half efficient under real conditions. This card has only 28 TMUs effectively. So, instead of a formal advantage on Nvidia’s part, the ATI solution is actually better as it has 32 full-featured texture processors whose architecture has already proved its worth in games. The RBE and memory subsystems of the competing cards from ATI and Nvidia are roughly equal, the GeForce being somewhat better when working with the Z-buffer.
Apart from games, the Radeon HD 4830 has advanced multimedia capabilities such as hardware support for decoding of VC-1/H.264. It also has an integrated audio core with support for multi-channel HD audio formats. The GeForce 9800 GT can only transfer S/PDIF input from the sound card to HDMI and supports hardware video decoding for H.264 format only (VC-1 decoding is done together with the CPU).
So, it seems that the GeForce 9800 GT will find it hard to compete with the new card of the Radeon HD 4800 series in terms of gaming performance as well as functionality. Our gaming tests will show you if this is indeed so. But let’s first take a closer look at the card.