After i remove ati smartgart still i can't change my agp speed to 8x.Removal tool from ati only can delete smartgart from start-run-smartgart.
How i can change agp speed manually???
How i know my radeon 9800xt run in agp 8x???
I suppose the best way is to Download either Sysoft software or rivatuner, bopth of these will tell you what your current AGP settings are. Also check the BIOS ( I know thats pretty obvious but) also ensure that you are running the most current version of your MoBo Bios. Earlier ones didn't always do what they were supposed to do. The other thing to check is your video card Manafacturers homepage, see if the have an FAQ you can quickly look up, your problem may not be unique.
Also ensure that you have the latest chipset drivers, VIA hypernion for VIA based boards or the .INF file if you have an Intel Chip. Foe some reason people tend to forget about the .inf file for the intel chipset ( if you have an intel based CPU you will have this chipset). This can be found in the downlads/drivers section for you specific motherboard. If you have an AMD CPU, then you will have most prob either an Nforce chipset ( Nvidia) or Via based board.
Hope that helps, let me know how you went on and if possible post full hardware specs for your setup, it helps if we have all the facts.