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NVIDIA GeForce 7800 GTX
by Damien Triolet et Marc Prieur
Published on June 22, 2005

A8N SLI Premium
For this test, we used the latest ASUSTeK nForce4 motherboard, the A8N-SLI Premium. It features two notable improvements compared to the A8N-SLI Deluxe. First, the noisy fan was replaced by a passive cooling system based on heat pipes, the AI Cool-Pipe, with a heatsink on top of the chipset connected to another heatsink via heat pipes located near to the CPU. The second heatsink is cooled down by the CPU cooler air flow. Of course in practice this solution is silent and the chipset doesn’t overheat even if we must say that our CPU cooler used in this test (a XP 120 with a 120 mm fan) is well suited for this kind of cooling system.

Another advantage is the replacement of the SO-DIMM port and accompanying board, used to enable non-SLI (x16 port and x1 port) to SLI configuration (two x8 ports) via a manual manipulation. The modification is now automatic according to the type of card inserted in the two PCI-Express x16 ports. Perciom switchs are used for this purpose. Would the A8N-SLI Premium be the perfect nForce4 SLI motherboard?

The test
For this test we have used a very high end computer to truly take advantage of the 7800 GTX and of crouse of the 7800 GTX SLI:

- ASUSTeK A8N-SLI Premium (bios 1005)
- AMD Athlon 64 2.8 GHz (soon to be introduced)
- 2x512 MB PC3200 memory 2-2-2
- Enermax 550W power supply
- 2 XFX GeForce 6800 Ultra PCI-E 256 MB / ForceWare 77.62
- 2 XFX GeForce 6800 Ultra PCI-E 512 MB / ForceWare 77.62
- 2 GeForce 7800 GTX PCI-E 256 MB / ForceWare 77.62
- ATI Radeon X850 XT / Catalyst 5.6
- Raptor SATA hard drive
- DVD ROM LG player

For this test we measured performance in 1280*1024, 1600*1200, and 1920*1200 (or 1920*1440 when this mode wasn’t available, like in Act Of War), with different graphic settings: standard, 4x antialiasing and 8x anisotropic filtering, and HDR if available. The significance of testing this type of graphic card in 1024*768 is minimal, so we preferred to increase the resolution to a higher one, which should please wide screen users.

CPU Limited ?
We will probably hear very soon that the GeForce 7800 GTX requires a powerful processor to be correctly exploited. Without being completely inaccurate, these remarks are more a crude generalisation as the graphic engines, the scenes they manage and the available graphic options lead to thousands of different loads.

Indeed we have to keep in mind that the overall rendering speed of a 3D scene comes from graphic processor speed in rendering the scene, but also the processor speed to calculate and send it.

So if scene A can be calculated at 60 frames/s by the processor but rendered at 90 frames/s by the graphic card under certain graphic settings, the final result will be 60 frames/s. This scenario is called « CPU limited », and means that the graphic card loses time in waiting for the processor. In this situation it´s good to increase the graphic settings (resolution, anti aliasing, anisotropic filtering, amongst others) to reduce the rendering speed to a closer level with the CPU. We will then no longer be "CPU limited" and it will be possible to have a higher graphic quality without a loss in framerate.

If you want to play at 90 frames/s, a graphic card change or reduction in parameter won’t help. You will have to lower a scene´s geometric or physic engine complexity, the animation or change the processor. The inverse situation is also possible, « GPU limited ». The best way to overcome this limitation is to reduce the graphic settings such as resolution.

The most important thing to know if a graphic card change is worth it, is to isolate your computer "Achilles’ heel". In a game if at some point the framerate isn’t sufficient, deactivate the most power hungry graphic options such as anti aliasing or anisotropic filtering and then reduce the resolution until you reach a decent framerate. If despite these changes the framerate doesn’t increase or it´s not enough, this is because the weakness is on the processor level (or the processor speed, which is also RAM speed).

The exception to rule is for limitations that come from a graphic card´s geometric power. But this only happens if you have a bottom of the line graphic card from two or three years ago. If images become blocked quite regularly, the problem may be a lack of central memory leading to a disc swap. You have to find out if disc access and the cuts in images are related (with your ear or eye via the HDD LED).

Apart from these exceptions, and the case mentioned above, changing the graphic card won’t bring any improvement. You will only have the same problem with a nicer image and we have seen better changes. In the case when reduction in graphic settings doesn´t improve fluidity, the graphic card is the origin of the problem and an upgrade is the answer.

If it´s not a great choice to couple an entry level processor with a high end graphic solution, perfect associations do not exist, because of the number of possible combinations. The best thing is to make an intelligent choice based upon the available information.

If we had to generalize, we would simply say that for current games, and even with high graphic settings, a graphic card of this type would not be pushed to its limits in 1280*1024 with an average processor. Generally, it is with resolutions such as 1600*1200 or 1920*1200 that gains are the most appreciable, even if this necessitates a case by case evaluation.

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