Good evening everyone!!
I'm a newbie on this things and I wanted to know wich is the cpu freq of the 328P of my arduino board, and how I can change it.
I've read that if I want to change it i've got to change the "fuses". I really don't understand this well.
Someone can help me?? 
PS: Sorry about my english!! ;D
I'm a newbie on this things and I wanted to know wich is the cpu freq of the 328P of my arduino board, and how I can change it.
Depends on what specific Arduino board you own. Most use an external 16mhz clock.
I've read that if I want to change it i've got to change the "fuses". I really don't understand this well.
Well if the fuses are set to use an external clock, then the speed of the process depends on frequency of the external crystal or resonator used. Changing the crystal frequency changes the processor's speed, no fuse changes required and 20 Mhz is max speed if using +5vdc Vcc. Most (all?) AVR processors also have an internal 8Mhz clock that can be used if the fuses are set to the proper values.
Note that if you change the speed of any Arduino board from it's standard speed, you must also modify some Arduino configuration files for all the software to run correctly.
Lefty
how I can change it.
Faster or slower? Why?
retrolefty:
Thanks for the answer . well, i have an arduino duemilanove. So if i'm not wrong and applying what you said it runs at 16MHz.
That question came to my mind because I notice that setting a software Freq of cpu of 20Mhz for the avr/delay library and make a _delay_ms(5000); wouldn't go over 5 seconds.
PaulS:
I don't have really the intention of changing it. It's only for knowing more about the AVR mcu's. If you know some tut's or doc about this, please post it.
Thanks one more time!!
I notice that setting a software Freq of cpu of 20Mhz for the avr/delay library and make a _delay_ms(5000); wouldn't go over 5 seconds.
Could also make loading your code with the installed bootloader tricky too.