ATi's tri opts turn themselves ON and OFF *automatically* in the current drivers (and don't exist at all in earlier Catalyst versions), in a programmed fashion, and *always* turn themselves OFF in the presence of colored mipmap tests, and other similar software conditions, which are the tests reviewers use to check trilinear filtering image quality. Therefore, if you do nothing apart from installing nVidia's drivers, nVx trilinear optimizations are turned ON by default (and the only way to turn them off is to check the appropriate check box in the nVx control paneland apply the change), so that's *why* ATi instructed reviewers to turn OFF the nVx tri opts when testing trilinear filtering IQ--because ATi's trilinear opts automatically turn themselves OFF under those software test conditions (colored mip tests, etc.) The fact that ATi's trilinear opts do indeed turn themselves ON and OFF automatically seems totally beyond your ability to understand, for some reason.