Control MCU frequency

[greywanderer012345]

I'm using an atmega328p and AVRStudio4. The MCU is supposed to be 8MHz, but it processes as if it is running at 1MHz, eg. the _delay_ms() function works correctly when F_CPU is defined as 1000000UL. Do I have some fuses set to slow it down or something? I had the $50 robot halfway built over a year ago, but had to get out of it for a while. I got the time to get back into robotics about a month ago. This is one of the things that has been bothering me. I halfway remember there being a way to slow the processor to save battery. Am I mistaken? Thanks for any help.

[newInRobotics]

As far as I know ATmega328P by default has CKDIV8 fuse on. If You clear it, uC will run @ 8MHz. Don't forget to change F_CPU to 8000000UL to get all timings correct. Don't touch any other fuses if You don't know what they do.

[greywanderer012345]

Thank you. That has to be the fastest, most thorough answer I've received. I knew it had to be something simple, but I was loath to start playing with the fuses. Thanks again!