Problems with low resolution modelines in X

Hello all, I've been adding some modelines for low resolution setups for xmame a few days ago but some are not accepted. An example: Modeline "320x224" 16.55 320 328 376 416 224 225 228 234 doublescan The XFree86 logfile states: (II) RADEON(0): Clock range: 20.00 to 400.00 MHz (II) RADEON(0): Not using mode "320x224" (bad mode clock/interlace/doublescan) My assumption (the mother of all f**kups) is that the modeline is not accepted due to the clock range starting at 20 MHz. Any idea on how I can decrease that 20 MHz? My old computer using a TNT chipset had no problems running these modelines, so I think they're correct in themselves. Regards, Pieter Hulshoff