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Nvidia GeForce 9600 GT

Architecture

The new G94 graphics core and the GeForce 9600 GT graphics card should be viewed as a correction of errors and flaws the developer committed when creating the G84 and the GeForce 8600 card.

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The positive trend is obvious: Nvidia has corrected all the flaws of the previous mainstream solution in the new chip. The number of execution subunits has been increased twofold, which is more than enough even in comparison with the ATI Radeon HD 3870/3850. If there are no application-specific optimizations for the superscalar Radeon HD architecture, the efficiency of the RV670’s 320 ALUs grouped in blocks of 5 ALUs may prove to be just as high as that of the 64 scalar processors of the Nvidia G94 chip. AMD’s chip supports DirectX 10.1 and Nvidia’s does not because such support is not yet called for.

There are 32 TMUs, but the texture processors are architecturally identical to those of the G84 and G92. That is, there are two filter units per each two texture address units. Theoretically, this ensures a high speed at texture sampling and filtering but only if anisotropic filtering is turned off. But today anisotropic filtering is enabled by every gamer who cares about image quality. Under real-life conditions such TMU architecture is only half as fast as the G80’s architecture with two filter units per one sampling unit. Thus, the G94 can be viewed as having 16 TMUs only, yet this is a step forward in comparison with the G84 and quite comparable to the texture-mapping performance of the ATI RV670 chip. The higher frequencies of the latter chip make up for its small amount of texture filter units: one such unit per each two address units. So, the two GPUs are roughly equal in this respect.

The raster operators have not changed since the G92 and there are as many of them as before. Thanks to improved compression techniques, Nvidia says their performance is 15% higher than the performance of the G80’s ROPs. From our tests of Nvidia’s GeForce 8800 GT/GTS 512MB we know that it is really so. The G92’s 16 ROPs are more than successful competing with the G80’s 24 ROPs. There are four ROP sections in the chip, which means four 64-bit memory access channels combining into a 256-bit external memory bus. This is one of the most significant improvements over the G82 whose 128-bit bus often proved to be a bottleneck. At a specified frequency of 900 (1800) MHz, the memory bandwidth is 57.6GB/s, i.e. the same as that of the GeForce 8800 GT 512MB. In other words, the GeForce 9600 GT is very unlikely to feel a lack of memory bandwidth.

New in the G94 chip is the controller of the DisplayPort interface integrated into the graphics core. Promoted by VESA, this interface is an alternative to HDMI and, as opposed to the latter, does not require licensing. DisplayPort supports the transfer of signal with a resolution of 2560x1600 pixels over a cable up to 3 meters long and the transfer of video signal with a resolution of 1080p over a cable up to 15 meters long. It can optionally transfer 8-channel 24bit audio stream with a sampling rate of 192kHz. Starting with version 1.1, the interface also features DisplayPort Content Protection developed by AMD. Conceived as a unified, easily expandable, royalty-free standard, DisplayPort may acquire high popularity in near future especially as it is supported by the leading hardware makers such as Intel, Dell, and Samsung.

The GeForce 8800 GT/GTS 512MB supported DisplayPort by means of an additional onboard controller, but the GeForce 9600 GT doesn’t need one, which simplifies the PCB design and makes the end-product cheaper. The integration of the DisplayPort and NVIO controller into the chip prevented the developer from reducing the amount of transistors greatly, although the new chip is less complex than the ATI RV670. Despite its 505 million transistors, the G94 doesn’t contain an integrated audio core as the RV670. The audio-over-HDMI feature is implemented in the GeForce 9600 GT in the same way as in some models of GeForce 8800 GT, i.e. by means of an S/PDIF adapter that connects the audio card’s output with the graphics card’s input.

The developer estimates the peak power draw of the new card at 95W, but we think it is going to considerably lower in real applications because the peak power draw of the Nvidia GeForce 8800 GT 512MB was measured by us to be only 78W. Overall, the Nvidia GeForce 9600 GT seems to be a well-balanced product and has a chance to become a new leader of the below-$200 segment – we’ll check it out in the gaming tests, of course.

Summing up, we have to say that although it seems to belong to the ninth GeForce generation, the 9600 model is no different from the eighth generation in terms of capabilities and architecture. In fact, the only advantage of the GeForce 9600 GT over the GeForce 8600 GT/GTS is performance. This naming system may sound confusing, but ATI has been guilty of it, too, with its Radeon X300, X600, X700 X800 series as well as with the Radeon HD 3000: it’s when a series would get a new number after but minor improvements.

 
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