NVIDIA GeForce 7800 GTX
The NVIDIA GeForce 7800 GTX
The G70 graphics core used in the GeForce 7800 GTX has more pixel pipelines than the NV40 it's supplanting as NVIDIA's flagship GPU, and boards based on the reference specification will have more memory bandwidth available as well. To give you an idea of where the GeForce 7800 GTX stands with respect to its main competition in these categories, we've put together a simple chart listing some raw performance characteristics for various cards.
* Some GF 6800 U cards now have a GPU core clock speed of 425MHz
As you can see, with 50% more pixel pipelines (16 vs. 24) and a higher clocked GPU (430MHz vs. 400MHz), the GeForce 7800 GTX has a peak theoretical textured fill rate that's 3.9Gtexels/sec higher than a GeForce 6800 Ultra (Pixel fillrate is lower because the G70 has only 16 ROPS). The 7800 GTX reference specification also calls for memory that's clock 100MHz (DDR) higher than a 6800 Ultra, which gives the GeForce 7800 GTX a 3.2GBps advantage in peak memory bandwidth as well. When compared to ATI's current flagship Radeon X850 XT Platinum Edition, the GeForce 7800 GTX is also superior in these respects. The GTX's fillrate is 1.66Gtexels/sec higher and it has a 600MBps advantage in the memory bandwidth category.
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Our initial impression of the GeForce 7800 GTX was that it appeared to be physically similar to a GeForce 6800 GT. The 7800 GTX and a 6800 GT are roughly the same size, and they both use a similar looking single-slot aluminum cooler with heat pipes and a radial fan. Like most 6800 GT cards, the fan pulls air in through the opening in the shroud and blows it across the heatsink's fins. Afterward, the air is expelled from the rear of the cooler and blown across the heatsink in the VRM. Upon closer inspection, though, it's clear that the GeForce 7800 is a different animal altogether.
As we noted in the chart above, the 7800 GTX's G70 GPU is clocked at 430MHz; its 256MB of Samsung GDDR3 RAM is clocked at 1.2GHz (600MHz DDR). And the 7800 GTX's PCB bares little resemblance to either a 6800 GT or an Ultra. The configuration of the card's VRM has been completely revamped. It's equipped with fewer capacitors than a GT or an Ultra, and a relatively large aluminum heat sink is visible on its MOSFET power array. The GPU cooler also functions a bit differently than previous generations. The fan used in the 7800 GTX's cooler is throttled based on the GPU temperature, but unlike older models that had only a few pre-set speeds for certain temperature ranges, the 7800 GTX's fan throttles more granularly on a "logarithmic" scale. This eliminates the abrupt change of pitch that some throttled fans exhibit when jumping from one speed to another. The configuration of the card's RAM is also slightly different. 256MB GeForce 6800 cards have all of their RAM packed onto one side of the PCB. The 7800 GTX, however, has only 128MB of RAM situated on either side of the card, which should help with heat dissipation.
Finally, GeForce 7800 GTX cards also sport dual-DVI outputs and a TV output, along with the same SLI connector found on the GeForce 6 Series of cards. The DVI and TV outputs can be used to power dual independent displays simultaneously, or four displays should two 7800 GTX cards be running in an SLI configuration.
