Speed step vs Turbo Boost vs CPU max speed?

[yoji]

Hi all ... noob question incoming (sorry)

I understand speed step (CPU will throttle down if not needed)
I understand Turbo boost (CPU will throttle up if needed)

So when my PC is 3.3Ghz with turbo to 3.6Ghz.... why is the CPU speed not just 3.6Ghz? since It seems it can throttle down to whatever... and up to 3.6Ghz completely dependent on processor load.. so the 3.3Ghz limit seems arbitrary?

I understand that the turbo does have the caveat "as long as its cool enough and has enough power" but that's the same as ever.. even if it at its rated max.. if it overheats it will slow down.

My actual CPU is overclocked to boost to 4.2Ghz.. with water cool it always cool enough.. so is it not in effect a 4.2Ghz CPU with speed step?

But you would expect Intel to claim max speed they can.. so I expect I am missing something.
What is it please?

Thanks in advance
Cheers

 

[dudeman509]

The base clock speed is usually the most efficient speed that specific processor model runs at for the amount of work it can accomplish per watt. The CPU will "turbo boost" to add more performance for a core or 2-3 cores that are being used heavily by an application to up the single-threaded performance of those cores to a point until the CPU reaches its maximum TDP, begins to heat up too much, or hits its maximum turbo boost speed.

Here's a good article explaining how it worked on the first-gen i-series chips (they have since drastically improved turbo boost speeds, starting with Sandy and further improving with Ivy Bridge). My Nehalem i5 only goes from 2.4 - 2.6; my Sandy Bridge ups from 2.3 to 3.0.

I think it is really very useful in laptops to conserve battery power.

http://www.makeuseof.com/tag/forced-induction-intel-turbo-boost-works-technology-explained/