Splinter Cell: Chaos Theory - SM3.0 & HDR

Seeing as Splinter Cell: Chaos Theory has a Shader Model 3.0 path, which is supportable by the new Radeon X1800's, we'll take a look at the performance difference between the two:




SC:CT - SM2.0 vs SM3.0 640x480 800x600 1024x768 1280x1024 1600x1200
XT SM2.0 135.0 126.6 106.1 77.8 58.5
XT SM3.0 133.2 124.1 102.1 74.5 55.8
XL SM2.0 120.2 104.9 82.7 59.6 44.5
XL SM3.0 117.4 101.7 79.9 57.6 42.9
 
% Diff between SM2.0 and SM3.0 640x480 800x600 1024x768 1280x1024 1600x1200
XT -1.3% -2.0% -3.8% -4.3% -4.5%
XL -2.3% -3.1% -3.4% -3.4% -3.7%

Presently on the Radeon X1800's there is a performance reduction for using Splinter Cell's Shader Model 3.0 path in relation to the Shader Model 2.0 code. Given that the patch that enables all the features that were bundled with the Shader Model 3.0 path for Shader Model 2.0 usage was written by ATI the code here is probably fairly optimal for them and its likely, given the early stage of development of these new boards, that the shader compiler optimiser hasn't been fully optimised for Shader Model 3.0 usage yet.

With the Shader Model 3.0 path Splinter Cell's HDR, utilising floating point blending, can be used:



SC:CT - Normal vs HDR 640x480 800x600 1024x768 1280x1024 1600x1200
XT - Normal 133.2 124.1 102.1 74.5 55.8
XT - HDR 127.0 111.6 87.9 63.0 46.6
XL - Normal 120.2 104.9 82.7 59.6 44.5
XL - HDR 106.1 88.5 67.7 48.2 35.5
 
HDR % Performance Reduction 640x480 800x600 1024x768 1280x1024 1600x1200
XT -4.6% -10.1% -13.9% -15.4% -16.5%
XL -11.7% -15.7% -18.1% -19.2% -20.2%

In this instance the performance penalty for enabling the HDR rendering mode is nowhere near as substantial as with Far Cry, with the XT taking a maximum performance hit of 17% and the XL 20%. Given these performance differences it would appear that bandwidth is an influencing factor here, as the XL has a lower bandwidth in relation to it fill-rate than the XT does and the XL has a higher performance penalty.