Hardware :: 640x480 Resolution With Radeon And KMS

I have on old Thinkpad T42 with the Mobility Radeon 7500 graphics chip. It used to work like a charm with the open source radeon driver, until KMS came along. It had no problems except for fullscreen being always black. I thought this is because I have an old card, and used 'nomodeset' in the kernel line, which strangely cranked up the memory usage and made the system choppier, but I managed. Today I was testing the use of an external monitor at home, and found out not only that it only works properly with KMS enabled, but fullscreen games work like a charm (e.g. DOSBox, which I use a lot).

After experimenting a bit, I found out that on the internal display (LCD), 640x480 produces a black screen, while others work as expected. so i set dosbox to use 800x600 as the fullscreen resolution, and it works. The problem is that there are a lot of games (and apps) that I use which provide no configuration options to set the resolution, so I end up with a black screen (when I'm using the internal display, of course). Bottom line: I'm not asking for anyone to fix my problems from a distance, basically blindfolded.