Hello, I am looking to build one of the usb programmers from adafruit. http://www.adafruit.com/index.ph... as I just got a new computer which has no serial port. and i have all the parts on hand and can burn the chip and everything. but I have one problem. I don't have any 10Mhz xtals. the closes thing i have is a 20Mhz. My question is. is it possible, via some fuse setting or some thing, to scale the clock down by 2. So the avr will run at 10Mhz instead of 20?