It’s no secret that ATI’s RV770 GPU, which first appeared in the Radeon 4870 and 4850 last year, is a performance beast. The spring refresh of the GPU, which offers increased core and memory clocks, along with a slight redesign of the GPU, tells an interesting story to anyone who isn’t yet running a second-gen DirectX 10 card (GeForce 2xx series or Radeon 48xx series). However, if you’ve already upgraded, there’s not much to get excited about here.

The Radeon 4890 is built on a 55nm process, just like the 4870 and 4850, but the company made significant tweaks to the architecture to accommodate higher clock speeds, which is evidenced by the fact that Diamond overclocks this board from 850MHz to 925MHz out of the box. Diamond also overclocks the card’s 1GB of memory 100MHz faster than the default, to 1,050MHz. The Radeon 4890 sports quad-pumped GDDR5 memory running on a 256-bit bus. The real stars of the Radeon 4890’s show are its pixel shaders, though, with 800 shader units running at the GPU’s core clock speed. The massive number of shader units gives the 4890 a significant advantage over comparable Nvidia cards in shader-limited benchmarks like Crysis.

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The Radeon HD 4830 at the heart of this card is a cut-down version of AMD’s second-best graphics processor, the RV770. The 4830 has 640 stream processors, compared to the 800 processors in a higher-end card such as the Radeon HD 4870.

The 4830 is designed to run at slower clock speeds, too, and PowerColor sets this model to operate its core at 575MHz and its 512MB of GDDR3 memory at 900MHz. These are pretty hobbled specs compared to those of the reference-design Radeon HD 4870, which boasts core and memory clock rates of 780MHz and 1GHz, respectively.

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Nvidia’s GeForce 9800 GT is really just a rebadged GeForce 8800 GT, which makes it the only card in our roundup based on a previous-generation GPU architecture: Nvidia’s 65nm G92. Despite its age, however, the G92 helped EVGA’s GeForce 9800 GT best PowerColor’s Radeon HD 4830—at least in terms of gaming performance.

EVGA runs the 9800 GT’s core at 600MHz, but takes full advantage of its 112 shader processors’ capacity for operating at much higher frequencies: 1,500MHz in this implementation. The card has a 256-bit memory interface to a full gigabyte of GDDR3 memory running at 900MHz.

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