OneWire and ClockSpeed

I have a project that uses onewire and some DS18B20 temp sensors. my board is an atmega168 at 16mhz to help reduce power i want to use the system clock prescaler to scale the clock down to 1mhz.

i have added an entry in boards.txt that specifies the 1mhz clock and everything seems to work fine except for the onewire stuff.

how might i have to modify the onewire library to get it to work at 1mhz?

thanks Jeff