Introduction

Thanks to a stellar launch earlier this week, NVIDIA’s GeForce 7800 GTX is poised to take the high-end 3D graphics market by storm. For the first time that we can recall, retail cards were (and still are) available online at the manufacturer’s suggested retail price of $599.99. And of course, the GeForce 7800 GTX is no slouch when it comes to performance. Even at stock frequencies, the 7800 GTX easily outperformed its predecessors in our GeForce 7800 GTX Performance Preview article, despite the fact that the board’s new clocks are only an incremental improvement over the GeForce 6800 Ultra.

Part of this is made possible thanks to the board’s new pipelines, up from 16 pixel pipelines in GeForce 6800 Ultra to 24 in the GeForce 7800 GTX, while on the vertex processing side, the GeForce 7800 GTX sports eight vertex units, two more than GeForce 6800 Ultra, which contained six units. NVIDIA has also incorporated improvements in each of these units to speed up processing time, as well as improved the chip’s ability to handle floating-point math, which is used increasingly more often in today’s shader-heavy games. NVIDIA has also improved the 7800 GTX’s ability to fetch textures.

GeForce 7800 GTX (top) ASUS GeForce 6800 Ultra (bottom)

EVGA e-GeForce 7800 GTX retail board and a reference 6800 GT PCI-E

On the manufacturing side, NVIDIA played it safe with GeForce 7800 GTX, relying on TSMC’s 0.11-micron manufacturing process. As we mentioned in our 7800 GTX preview article, 0.11-micron is a die shrunk version of TSMC’s 0.13-micron process (only without low-k dielectric), and is considered TSMC’s value process, designed for low costs, rather than high clock speeds. This is why both ATI and NVIDIA chose 0.11-micron for their mainstream and value products, the GeForce 6600/6200 family, and the RADEON X300/X600/X700 series. The cost savings afforded by 0.11-micron played a critical role in allowing ATI and NVIDIA to integrate more pipelines into the GeForce 6600 and RADEON X700 in particular.

NVIDIA decided to use this process again for the 7800 GTX, rather than take a risk on TSMC’s newer, smaller 0.09-micron process, which is intended for higher clocks. NVIDIA got burned during the 0.15-micron to 0.13-micron transition with GeForce FX (from GeForce4), with the part never yielding well at the clock speeds intended. NVIDIA likely didn’t want to take a chance again, opting to play it safe instead, even though that limited them to lower clock speeds. NVIDIA’s engineers must have felt that the shader optimizations they’d implemented, plus the additional pipelines would be enough to get them by, and right now that strategy appears to be the right one, as there are rumors that the launch of ATI’s next-gen chip, R520, has been delayed due to poor yields.

The 7800 GTX cards

Reflective finish on EVGA card

The only downside to 0.11-micron is as a value process, it doesn’t contain the performance optimizations found at 0.13-micron and 0.09-micron that allow for high clock speeds. You can see this today on cards built on 0.11-micron, such as the X800 XL. Our overclocking results with graphics cards based on this chip in the past have been rather mundane, with none of the six cards we tested in our RADEON X800 XL Roundup overclocking to more than 10% of their stock clock speed (one of the cards barely overclocked 5%). On the NVIDIA side, we had a little more luck with the GeForce 6600 GT cards used in our 6600 GT AGP Roundup, but in that case, we’re dealing with a much smaller 8-pipeline chip, with only 146 million transistors. GeForce 7800 GTX is much bigger than 6600 GT, and contains twice as many transistors at 302 million.

With this in mind, we were worried with how well the chip would scale to higher clocks. That’s what we’re here today to find out!