That was the thing we were missing, the one aspect of SP1 that might explain the performance delta: it introduces DX10.1, and the X2 is a 10.1 part. As seen above, DirectX in its latest incarnation brings some nifty features that might translate into better AA performance and quality-we were seeing both with SP1 installed. Could it be that AC is the first title to support DX10.1?If that is the case, why was it not actively advertised? Since it seemed we had an enigma on our hands, there's was no easy way out other than to investigate