Dothan Pentium M cpus and Banias Pentium M cpus BOTH run at 400mhz fsb.
They use the same 855PM chipset which can accept PC2100, PC2700, and PC3200
Though the max speed PC3200 will run at will be PC2700. (333mhz)
Dell is always a rip when it comes to memeory, they put PC2100 (slow) in a lot of 600Ms when it should have been PC2700.