If using Gigabyte board and F4beta bios and later, just think of turbo as an extra multi. So for i920 if you want to use 20 multi (stock) turn turbo off. If you want to use 21 multi, set turbo on, and you now have a permanent 21 multi (though bios still says 20).

If you have a board that enables TDP limits...read intels white paper, but GB bios ignores TDP, current, and temp limits so below paper does not apply.
http://download.intel.com/design/pro...=tech_tb+paper

Edit: my god Im a slow typist...3 posted before me..lol