By the way, the G71 is the second desktop graphics processor to work at as high a frequency as 650MHz, ATI’s R580 (Radeon X1900 XTX) having been the first. Well, the entry-level Chrome S27 processor from S3 Graphics works at 700MHz but it is obviously a much simpler chip than the top-end solutions from ATI and Nvidia. So, although Nvidia cannot claim it produces higher-frequency chips, it has got even with ATI in this respect. We’ll see in the gaming tests section how the higher operating frequencies affect the performance of Nvidia’s new flagship product.

It seems the G71 differs from its predecessor in clock rates and tech process only, but take note of the dramatically smaller number of transistors the chip is made up of. The GeForce 7900 is 24 million transistors “thinner” than the GeForce 7800! This makes it the simplest graphics processor in the top-end sector today (fewer transistors were only employed in the previous-generation GeForce 6800 (NV40/45) and Radeon X800/850 (R420/R423/R480) processors). Combined with the thinner tech process, the fewer transistors mean a smaller die area and better thermal characteristics of the chip. The manufacturing cost is reduced, too, since more dies can be made out of a single silicon wafer.

Unfortunately, we do not know exactly how Nvidia managed to strip the chip of so many transistors without losing anything in its functionality. We do know that this was made by redesigning the pixel processors area of the chip. 24 million transistors is quite a big amount, so we are left to wonder what was cut off from the new GPU. The G70 may have originally been redundant or perhaps Nvidia did manage to optimize the pixel processors design so marvelously.

The chip now also incorporates two dual-link DVI controllers which have previously been available in Radeon X1000 series GPUs only. So, Nvidia’s new graphics cards do not need an additional chip to implement a dual-link DVI interface which is used with high-resolution TFT displays like the 30” Apple Cinema HD. CRT displays are supported exactly as before: two 400MHz RAMDACs allow using display modes up to 2048x1536@85Hz. It is unnecessary to improve anything in this area since CRT monitors are currently leaving the consumer market.

Nvidia returns in the GeForce 7900 to the idea of clocking different GPU subunits at different frequencies: the pixel processors and ROPs of the GeForce 7900 GTX and GT work at 650 and 450MHz, respectively, and the vertex processors at 700 and 470MHz, respectively. Considering that the speed of modern games is not generally limited by the speed of the vertex processors, this approach shouldn’t tell negatively on the performance of the new graphics cards.

This shouldn’t affect their thermal and electrical characteristics much, either. Nvidia declares a peak power consumption of 120W for the GeForce 7900, but the chip consumes that much power only when all its transistors are working simultaneously. This has nothing to do with real operating conditions, of course. Considering the smaller amount of transistors and the use of a new tech process, we can expect the GeForce 7900 GTX to be more economical than the GeForce 7800 GTX 512. We’ll check this out shortly, but now let’s take a closer look at the new card.