Z/Stencil Performance

Over the past two generations NVIDIA's architectures have had the capability to double up the number of Z writes when no colour writes are needed by doubling up the colour ROP as a Z ROP (making a "combined" ROP) to operate in conjunction with the standard Z ROP. Whilst this doubles up the Z write performance, a side effect of this is that it can also double the stencil write performance as this is usually generated off the Z ROP. Here we'll test to see if GammaChrome S18 has a Z/Stencil performance higher than its pure pixel fill-rate.

With this test we see that the GeForce 6's are achieving nearly 90% greater Z rendering performance than their theoretical pure pixel fill-rate's, highlighting the fact that they can output twice an many Z writes as colour writes. Whilst the S18 GammaChrome isn't achieving as close to double the performance of its single texture fill-rate it is significantly higher suggesting that it may have some similar capabilities as that of the GeForce's.

Game Test 2 in Futuremark's benchmark application 3DMark03 uses an early Z pass and stencil buffered shadows, so we'll look at the rendering performance of the S18 Nitro in this test.

We can clearly see the importance this test places on Z and stencil performance by comparing the 6600 and 6200's performances against the X600 PRO's - the 6200 has a lower fill-rate and, from all previous tests, lower performance and yet here, by virtue of its double Z/Stencil performance it is able to outperform the X600. The S18 Nitro, though, is able to keep pace with the 6600 fairly well, indicating that the Z fill-rate performance tested before translates well into situations that have high reliance on Z/Stencil performance.