|By the way, in the real world, a video chipset running in 8X AGP mode does NOT perform twice as good as the same video chipset does in 4X mode. |
"All AGP 8x cards work with 4x boards."
That's not quite right guys.
All AGP 8X capable video chipsets also support 4X mode, but NOT all video chipsets that support 4X or 8X AGP modes can be used in mboards that support 4X or 8X AGP modes.
Video chipsets capable of 4X or 8X AGP modes that were first released earlier often also support 1X and 2X AGP modes.
The 1X is often omitted because very few mboards / main chipsets were made that support only 1X AGP mode.
The Radeon 9250 video chipset supports 1X / 2X /4X / 8X AGP modes.
Some mboards that support 4X AGP mode, or 4X / 8X AGP mode, CANNOT use an AGP video chipset that supports 1X / 2X modes ( they use 3.3v ) - doing so will DAMAGE the video card AND the AGP slot's circuits.
READ the manual for your mboard model ! If that applies, there will be a WARNING message in the manual regarding that !
This shows which Radeon video chipsets support which AGP modes:
If your mboard model cannot use AGP cards that support 2X mode (3.3 volts) , then you need a Radeon video chipset 2X is not listed for.