P4S8X and AGP 8X

I have Asus P4S8X-X (Sis 648 chipset) and GF4 Ti4200 8X , My question: why SiSoft Sandra & Nvidia Bios Editor reports my AGP Transfer Rate is only 2X ?? .

Sis 648 is designed to handle AGP 8X, and I have set in BIOS Menu 8X AGP too. I use Windows ME, and Nvidia Detonator drivers v. 42.30 WHQL. My VGA is AGP 8x.

Can somebody help me?? especially P4S8X owners??

Hello??? people??? help me... please.

I had to install the SIS AGP drivers to get 8X AGP to work...