Sandybridge, Speedstep/turbo and you

Not much to report here, just a very strange thing I found.

If you did not know it, you can choose to boot your system with more than one core of your cpu. The default is one core. In the case of a sandybridge with hyperthreading, you have up to 8 cores.

By using MSCONFIG you can can set how many cores to boot with. With my core2duo system, I set it to 2 cores and it did make a noticeable difference. I enabled it to 4 on my new 2600k system, and once I did, speedstep and thus turbo stopped. The cpu ran at its default 3.4 ghz rate, and did not go up nor down.

I was not aware that option would do such a thing, as I though the BIOS handled the speedstepping independently of OS. Evidentily not.

Wierd.

Sul.

 

By default your OS boots up with one core while it initiates some things with CMOS and then after that all cores are used.

 

I can confirm messing with msconfig's control over the amount of processors used at boot will show up strange happenings. When I first got my I7 2630QM laptop I followed a Win7 tweak guide - I had 8 cores to choose from in MSCONFIG - oh yipeee 8 cores to choose from this will fly at boot (I thought). The default MSCONFIG setting was showing just 1 core - So I enabled 2 cores to see if it would be stable, the guide recommended 2 or 4 (looking back I can see how outdated this tweaking guide is). When I checked CPU-Z it only showed up the 2 cores, same with taskmanager, and turbo had gone AWOL.

Changing the MSCONFIG boot processor setting to 0 will reset the default cores - Which is what I did. Get Windows 7 to detect your new multi-core processor

tweaking-myth-increase-boot-performance-for-multi-core-users-with-msconfig/

Gotta be careful with outdated tweaking guides.