NVIDIA GeForce 8800 GT (G92)

Part 2: Features, Synthetic Tests

Direct3D 10: Vertex texture fetch rate

Vertex Texture Fetch tests measure the speed of many vertex texture fetches. These tests are similar, and the correlation of their results in Earth and Waves tests must be also similar. Both tests use displacement mapping based on texture fetches. The only major difference is that the Waves test uses conditional branches, while the Earth test does not.

Let's analyze the first test (Earth) in Effect detail Low mode:

All three graphs demonstrate a similar picture of performance. Performance correlation between top solutions and Mid-End graphics cards remains the same, it's approximately two times between the GeForce 8600 GTS and the 8800 GTS, up to 1.5 times between the GTX and GTS cards. There is quite a big performance difference between the GeForce 8800 GT and GTX cards. It cannot be explained with the different number of texture units. This test seems to be affected by memory bandwidth, which differs significantly in these products.

Let's have a look at results of this test with more texture lookups:

The situation hasn't changed much. The GeForce 8800 GTX is still in the lead, followed by the GeForce 8800 GT (it lags slightly behind because of the difference in the number of TMUs and memory bandwidth). Then go the RADEON HD 2900 XT and both GeForce 8800 GTS cards. The GeForce 8600 GTS falls far behind and reveals all its weaknesses.

Let's have a look at results of the second vertex texture fetch test. The Waves test executes fewer texture lookups, but it uses conditional branches. The number of bilinear texture lookups in this case reaches 14 (Effect detail Low) or 24 (Effect detail High) per each vertex. Geometry complexity changes just like in the previous test.

The Waves tests demonstrates a similar situation (as in the Earth test), but the difference between the G92 and G80 has grown bigger. The GeForce 8800 GT is sometimes outperformed by the GTS cards and by the RADEON. But as geometry complexity grows, it restores its strength, being outperformed in the most complex test by less than 20%. Let's analyze the second mode:

These results agree with those demonstrated in the previous tests, only the RADEON HD 2900 XT falls back relative to NVIDIA solutions. The GeForce 8800 GT generally copes well with vertex texture fetch tests. When geometry complexity is low, its performance is limited by lower memory bandwidth. When the amount of geometry data grows, performance of this card comes close to the GeForce 8800 GTX.

Conclusions on the synthetic tests

• To all appearances, the G92 architecture hasn't changed much since the G8x. It's notable for high computing performance, so this card is designed for modern and future applications with lots of complex shaders of all types. High efficiency of unified processors, many TMUs and ROPs, as well as high operating frequencies allow this GPU to demonstrate excellent results in all synthetic tests. The GeForce 8800 GT performs almost on a par with the more expensive GeForce 8800 GTX, coming close to this card as the load grows and even outscoring it in rare cases.



• Conclusions on shader tests for the GeForce 8800 GT: the new Mid-End card from NVIDIA copes well with complex pixel, geometry, and vertex shaders. The architecture of this GPU was improved (modified TMUs). As a result, the GeForce 8800 GT sometimes outperforms the GeForce 8800 GTX, as it has higher theoretical texel rate in certain conditions.



• The only weakness of the G92 and the GeForce 8800 GT is a narrower memory bus and consequently lower memory bandwidth. That's what is badly needed in some tests to perform on a par with the GeForce 8800 GTX or better. However, its memory bandwidth is quite sufficient for a Mid-End solution, the same applies to its performance.