hardware usage by arduino.

Hi I'm new to arduino but have been programming the MSP430 for some time (with mspgcc).

I've been looking through the documentation and am having a hard time figuring out which hardware is used by the libraries and which is not.

Is there a list of which hardware is used by the Arduino "API"? So I could see for example that the tone() function uses timer XX.

If I ignore all the library functions is it safe to use all the hardware present in the ATMega or is so some of it used by default?


EDIT: I found main.cpp and init() in arduino-0021/hardware/arduino/cores/arduino/. There is initialization code that sets up timers 0-5. It appears mills uses timer 0 and 1-5 are for PWM.