Wiring Lib

Hi to all! Where can I find all the default settings of MCU registers and frequency setted by the Arduino environment? I mean those ones that I can find in the AVR IDE. Like the lib which describe that I'm using a 16Mhz quartz instead of 8, or the register that by default use the internal oscillator: Arduino have to set this to external for using the 16Mhz...well, I'd like to find this re-"default" setting.

I'm conscious about thing that I can set every register in my own code, but i'm looking for codes/settings that works behind my code by default without using an AVR IDE...it's too heavy for my purposes.

Thanks!! :D

I mean what's the toolchain process used? Or where it's published?