A little bit of info please


I'm very new to arduino but reasonably good with electronics. I bought an attiny 84, 8bit @ 20MHz for a project I'm making, see link ( http://ie.farnell.com/atmel/attiny84a-pu/mcu-8bit-attiny-20mhz-dip-14/dp/1972172?CMP=i-bf9f-00001000 ).

My question is.... can I run this chip at 20MHz just by choosing the correct board in the arduino IDE or do I need an external osc ? and if so what is the max speed it can be run at without one. Thanks

Option 2 (external something: resonator, crystal + capacitors, oscillator).

8 MHz.

Thanks Coding Badly for your help