The Duron is running on a 100MHz Bus (200MHz DDR), so it´s not surprising that it can´t handle anything higher than 112MHz (224MHz DDR). It´s like getting your Thunderbird 266, from 133MHz to 145MHz, which isn´t bad. As far as I know, only the new Durons, with the Morgan-core, can run on a 124-150MHz Bus. It all depends on the quality of the processor, higher quality means higher FSB, higher clock rate and the possibility of running on a lower CPU voltage.
I had a cool sig. ready, but my dog ate it!