Attiny85 @ 16MHz and at lowest power

Other Hardware 3rd Party Boards
1

I have a split question with the attiny85. First, when using the ATtiny85 16MHz bootloater, how to I set up the crystal? And is there a more accurately timed way to run the attiny85, like with a different crystal?

My other question is going totally the other way. I was also interested in using the attiny85 to power a RGB led with a couple coin batteries, is it possible to get it low enough power for this to be doable? How slow can the attiny85 get while still being programmable with the arduino environment? (edit: more specifically, I want to randomly fade between colors and possible other basic LED related things)

Also any suggestions on efficient power supply would be nice. I'm looking to have the attiny and led fit inside a small necklace locket. Any very tiny rechargeable options?
(edit: the tiny library goes down to 1MHz, does anyone know what the power consumption is at that? I can test it myself later on if not... Can it be taken even lower?)

Thanks

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  1. if you have two questions you should create two posts
  2. Yes, you can time more accurately. However unless you tell us how accurately we can not tell you if you should use a higher quality crystal, a RTC, an OXCO, a cesium clock or a gps disciplined time normal.
  3. If you tweak the configuration accordingly you can get as slow as you want. However in terms of reduced power consumption it does not pay off to much to go below 1MHz. Anything below 128kHz does not deliver any reasonable gains. The key is to sleep the CPU as much as possible.