Sandy Bridge & Turbo Boost

[bntran02]

I'm running on 2500k OC'ed to 4.4Ghz with turbo boost enabled.

Can someone explain to me how the turbo boost works in an overclocking situation?
e.i:
1) Does it run at 4.4Ghz when idle and then turbo boosts upward when necessary?
2) Is 4.4Ghz my turbo boosted max?
3) Does my overclock "window" just move from (3.3 - 3.7Ghz) to (4.0 - 4.4Ghz)

If I am any where correct then can my clock "window" be adjusted to be very wide like maybe 1.6Ghz to 4.4Ghz for example

Thanks for the replies

 

[Mark R]

SB will automatically choose the lowest possible speed, as long as any one core on the CPU is not fully loaded.

Under load, any and all cores will clock up to their maximum possible speed, given certain limits. The limits depend on core temp, power consumption, and time spent at boosted speed.

The 'normal' core speed is the speed that the CPU is designed to run at 24/7, with stock cooling under max load. If the CPU is under load, the clock won't drop below that speed unless temperatures are critical.

However, SB will always try to 'turbo' clock the chip whenever any a core is fully loaded, subject to certain limits (e.g. core temperature, power consumption limits, etc.) E.g.the turbo function won't raise the clock if the CPU power consumption would go above 95 W.

The normal way to overclock a SB, is simply to tell give the turbo system higher limits - higher max speed, and higher power consumption limit.

So, if you've clocked it up to 4.4 GHz, by setting a max turbo of 4.4 and ridiculously high power limit - then you basically get a super-wide frequency range, just as you suggest.

 

[Kenmitch]

If I am any where correct then can my clock "window" be adjusted to be very wide like maybe 1.6Ghz to 4.4Ghz for example

Yes dependant on bios settings. Which mb are you using?

 

[Ratman6161]

I'm running on 2500k OC'ed to 4.4Ghz with turbo boost enabled.

Can someone explain to me how the turbo boost works in an overclocking situation?
e.i:
1) Does it run at 4.4Ghz when idle and then turbo boosts upward when necessary?
2) Is 4.4Ghz my turbo boosted max?
3) Does my overclock "window" just move from (3.3 - 3.7Ghz) to (4.0 - 4.4Ghz)

If I am any where correct then can my clock "window" be adjusted to be very wide like maybe 1.6Ghz to 4.4Ghz for example

Thanks for the replies

You don't have to worry about it. It will do this automatically and Sandy Bridge cpu's always run at 1.6 Ghz when idle. For example I currently have my 2600K clocked at 4.1 GHz. But it is almost never actually running at that speed. At idle it's at 1.6 Ghz and when something demands cpu power it seems to always turbo boost at least one level above that.

 

[sm625]

Under load, any and all cores will clock up to their maximum possible speed, given certain limits. The limits depend on core temp, power consumption, and time spent at boosted speed.

Has this actually been tested and verified by anyone? With LN2 or something like that? If it really worked that way then we should see faster stock performance on LN2.

 

[bntran02]

My board is MSI P67A-G43

According to Anand:

http://www.anandtech.com/show/4083/...-core-i7-2600k-i5-2500k-core-i3-2100-tested/3

and several post around the web my understanding is this:
When idle the CPU will be at 1.6Ghz
Under light loads all cores will be active at 3.3Ghz
Under heavy multi threaded apps all cores will be active and turbo-ed 4.0Ghz
And depending on the number of cores active their clocks will be turbo-ed to:
4 Cores @ 4.1Ghz
3 Cores @ 4.2Ghz
2 Cores @ 4.3Ghz
1 Cores @ 4.4Ghz

is this correct?

Thanks again for the replies

 

[Crap Daddy]

Mine is at 4,2 with turbo. Here's how it goes after my observation, 1,6 idle - desktop, when needed the turbo kicks in to the OCed value, 4,2 on one or more cores.

 

[Seero]

I'm running on 2500k OC'ed to 4.4Ghz with turbo boost enabled.

Can someone explain to me how the turbo boost works in an overclocking situation?
e.i:
1) Does it run at 4.4Ghz when idle and then turbo boosts upward when necessary?
2) Is 4.4Ghz my turbo boosted max?
3) Does my overclock "window" just move from (3.3 - 3.7Ghz) to (4.0 - 4.4Ghz)

If I am any where correct then can my clock "window" be adjusted to be very wide like maybe 1.6Ghz to 4.4Ghz for example

Thanks for the replies

Unlike in the pass where people needs to increase multiplier or FSB to OC, SB is designed for people to OC only when the CPU is under load. That means, at idle, it operates 3.3/2 ghz, which is around 1.6Ghz. Let say you increased the Turboboost multiplier to 44x from 38x while base clock is 100, without touching anything else except voltage, then when the CPU is under load, the mobo will increase both voltage and multiplier from 33x(base clock) to 40x-44x(OC clock). Once the thermal cap is reached, the CPU goes back down its base voltage and multiplier to 33x.

If cooling is sufficient, the CPU will stay at OC multiplier, which is 44x in this case. Turbo Boost 1.0 means the CPU OC itself by increasing the voltage defined to keep the CPU stable under full load at the defined OC. Turbo boost 2.0 means instead of just 1 level of OC, it has 4. People can define 4 seperate OC profile depending on the usage of the CPU, namely 1-4 core.

So let say you can get a stable clock (4.0ghz) with all 4 core at max load, then it means you should be able to handle 4.4ghz with only 2 cores under load and 4.8ghz with only 1 core under load.

By specifying the OC multiplier to 44, it means 44x,43x,42x,41x multiplier for 1,2,3,4 cores utilization. You can manually specify multipliers for each individual profile with its own multiplier and voltage so the profile will adjust dynamically based on the load of the CPU.

I assume that the cap is somewhere between 90-95c. Once the CPU reaches that temp, OC stops. Once OC stops, it doesn't kick in again for a while. I managed to have my cpu go beyond 98c and core temp shuts down the PC. After that CPUz states that the multiplier stays at 33x under prime95 while I set it to 52x. So if you managed to keep temp under 80c with prime95 on all cores, then your cpu will operates at OC multiplier at all time.

To answer your question, with sandy bridge, you do not overclock the base multiplier, you overclock the turbo boost multiplier. 4.4Ghz is no where near max, but it all based upon the setup, cooling, and the quality of each component.

 

[betasub]

^ Thanks for the SB-turbo explanation, Seero!