Disabling cores on Sandy Bridge i7's?

I can't seem to find a guide on how to do this. I've heard that disabling is possible through msconfig but re-enabling the cores is trickier. Laptop in sig

 

Maybe this will help
windows 7 - How to disable 2 cores on a quadcore i7? - Super User

 

Won't they disable themselves when they're not needed? I thought that's how Turbo Boost worked.

 

thats how speed step works, but yeah the cpu does that automatically

 

Neither Turbo or Speedstep disable cores. C-states can essentially power down cores through gating and that's usually controlled via the OS. IMO the BIOS should be used to properly disable cores.

 

I'd just leave it. If you disable them then you won't have the option of using them even if you want to whereas you have essentially the same thing with core parking but you still have the option to use all cores if you need them.

The difference between parking cores and actually disabling them will only be 0.5W or something along the lines.

 

I think you'll find that with most windows clients with core parking the default use is with hyperthreading where one of the threads of each core is parked and not cores themselves. This helps schedule loads per core and does very little for power saving. In other words 4 heavily loaded threads on a 4C/8T CPU will hopefully end up running each thread on separate physical core to help maximize performance.

 

well since powergating is in speed step, its actually correct what I said

 

I did a battery test with i7-2630qm both at full four cores, and disabling two cores. It made next to no difference in battery life, so there really is no benefit. Only time it will matter is if you're running the CPU near peak, but most laptops gimp the CPU performance on battery anyhow so it still wouldn't matter.

 

Mr MM where are you getting this info from? Speedstep as it's name implies, changes the speed of the processor from LFM up to turbo. Maybe you're definition of power gating is different to mine where it means turning of power to the core components.

HTWingNut that's interesting, I'm still on C2D for the laptop and probably will not be upgrading until Haswell unless something goes TU. With the C2D there is an undocumented way to turn of one of the cores and while using DOS which doesn't use SMP the results showed power draw was much improved this way and that unless it was done that way would make very little difference under Windows using msconfig. Since Nehalem there have been great steps to improve on power saving so probably not so important for todays processors.

 

Well I really love the NP8130 but its battery life is horrible. And I'm more interested in battery life, but 2.5 hours just wasn't cutting it for me.