On Mon, 10 Mar 2003, Steve Thatcher wrote: The original XT hard disk controller (Xebec) could handle certain geometries of 5, 10, 15, 25 MB with a trivial hardware mod. NO software changes required. Near the center of the board are eight solder pads. If you install a dip switch there, you get 4 different drive types for each of the two drives. Both off, the default, is 10 meg (306 cylinders, 4 heads). But, if you wanted some other geometry, (or were unable to solder a switch or jumpers on, then you needed to do some patching, preferably to the ROM on the controller card.