I am running Fedora Core 6 on Thinkpad T42, which has a Radeon 7500. For the internal display it works very well with its highest resolution 1024x768. But when I am using an external display (such as Dell 1702FP), I cannot switch to a highest resolution. In FC3, it will automatically adjust to its highest resolution after plugging in.

So, is there any solution for my case?