Nvidia GeForce 7900 GS

History and Specification

When replacing the GeForce 7800 series, based on the then revolutionary G70 processor, with the GeForce 7900 family that uses the more progressive 0.09-micron G71 chip, Nvidia discovered a gap in its product line-up right in the very popular price category of $199. The gap stretched from the GeForce 7600 GT to the GeForce 7900 GT that belonged to price ranges of $149-199 and $249-299, respectively. There is indeed an abyss between these two graphics cards in terms of price as well as of technical characteristics. The former has 12 pixel shader processors, 12 TMUs and a 128-bit memory bus whereas the latter uses a 256-bit memory bus, has 24 TMUs and 24 pixel processors. A $199 solution must be somewhere in between.

In the ATI camp, this niche had been filled with the Radeon X1800 GTO which was subsequently replaced with the Radeon X1900 GT. And now the latter is going to leave room for the Radeon X1950 Pro. The GeForce 7600 GT was competitive against the first solution from the three, but it looks downright weak against the Radeon X1900 GT or Radeon X1950 Pro. After all, it belongs to a lower price niche. So, Nvidia wanted a graphics card that would be able to challenge ATI Technologies’ solutions right in the $199 sector. How did they do that?

In our review of the XFX GeForce 7600 GT XXX Edition card we found a disabled quad of pixel processors in the G73 chip. By one supposition, the disabled quad was a kind of reserve Nvidia might use to quickly respond to the rival’s releasing a new mainstream graphics card. We won’t probably know if it was so or not because Nvidia took another approach. Instead of improving upon the G73, they cut down the G71. In other words, the GeForce 7900 GS resembles the GeForce 7800 GT which had also been made out of the G70 chip with some of the pixel and vertex processors disabled.

The solution looks logical to us. The G71 is simple even in comparison with the G70, let alone the ATI R580, and is, accordingly, cheap, even though it doesn’t look too advantageous in comparison with the RV570. Moreover, Nvidia didn’t have to design a new PCB because they already had the simple and cheap PCB from the GeForce 7900 GT. That PCB suited fine for the GeForce 7900 GS with its fewer active GPU subunits. So, the new graphics card has 20 pixel pipelines and 7 vertex pipelines. That is, it was made out of the GeForce 7900 GT by disabling one quad of pixel processors and one block of vertex processors. You can learn more about the GeForce 7900 GS specs from the table at the beginning of this review.

The GPU and memory frequencies were left intact. Having such specs, the GeForce 7900 GS looks a rather fearsome rival to both versions of Radeon X1900 GT as well as to the new Radeon X1950 Pro. Let’s scrutinize this card closely now.

PCB Design and Cooling System

The photographs show quite clearly that the etalon sample of the GeForce 7900 GS card doesn’t differ visually from the GeForce 7900 GT:

The cards use identical PCBs and coolers, but the GeForce 7900 GS is a mainstream product and is not covered by Nvidia’s strict policy concerning the purchase of ready-made cards as is the case with the higher-performing GeForce 7900 GTX and GeForce 7950 GX2 models. So, we can expect to see original models of GeForce 7900 GS built on non-reference PCBs designed by the graphics card manufacturers on their own.

The main frequency of the GeForce 7900 GS GPU is 450MHz, but its vertex processors work at 470MHz. In these parameters the card doesn’t differ from its ancestor. As we said above, there are 20 active pixel processors (5 quads) and 7 active vertex processors in the GeForce 7900 GS. The other processors are disabled on the hardware level by cutting up the bridges on the die package with a laser. It means it is impossible to unblock those subunits and transform the GeForce 7900 GS into a GeForce 7900 GT. But considering the polished-off tech process, most of the chips that go into GeForce 7900 GS production are likely to be fully functional and without any defects. So, it is probable that there will appear “overclocker-friendly” versions of this graphics card in which some of the subunits are disabled on the software level and can be unblocked by using an appropriate BIOS or with RivaTuner.

An overwhelming majority of graphics cards of a high enough class tested in our labs have been equipped with Samsung’s memory, but the GeForce 7900 GS is an exception. This card carries eight Hynix HY5RS573225A GDDR3 chips, 256Mb each. The chips’ FP-14 suffix denotes the appropriate access time and a rating frequency of 700 (1400) MHz. The real frequency the memory works at on this card is the same as on the GeForce 7900 GT, namely 660 (1320) MHz, and provides a bandwidth of 42.2GB/s.

The GeForce 7900 GS is considerably better than both versions of Radeon X1900 GT in this respect, but not than the Radeon X1950 Pro. We should also keep in mind the more efficient ring-bus memory controller of ATI’s graphics cards.

The GeForce 7900 GS comes with the same cooler as the GeForce 7900 GS is equipped with. It consists of a simple copper base to which a folded sheet of copper is glued. This heatsink is topped with a small blower, about 45mm in diameter. The whole arrangement is covered with a plastic casing and is fastened to the PCB with four spring-loaded screws. The solution is not very efficient, but does its job well even on the GeForce 7900 GT considering the low heat dissipation of the G71 chip. So, the cooler won’t have any problems on the 7900 GS which has some of the subunits disabled. The memory chips are not cooled, just like on the GeForce 7900 GT.