# Turbo Boost... How does it work, and how to overclock?



## wkw427

Please correct me if I'm wrong in my understanding of this... But this is what I've gathered so far... 
Turbo boost dynamically changes the clock speeds depending on load. CPUZ shows my cores at 1.6 ghz when idle, up to 3.3 when under load. 
It also is able to turn off one or more cores when more processing power is needed on one core, so that it can up the clock speed on a single core

Is this correct? I've tried playing around with some of my bios settings (GA-Z68XP-UD3 board, i5 2500k cpu) to change clock speed.. 
I've tried to change the multiplier from 33x (default) to as low as 16x, or 40x. No change in windows, at all. Except sometimes I don't post. If I change it to 30x or 35k, no change as far as I can tell.
I've enabled turbo boost, but when I run prim95 I don't see any cores slowing down, nor does cpuz show a clock speed/multiplier above 3.3ghz/33x

I have disabled three cores, and windows system properties shows i5 2500k 3.3ghz @ 5.7ghz... but again, cpuz shows only 3.3ghz when under load.




Again, this is just to quench my curiosity. I have no interest nor any need to OC. In fact, for the past.. seven months I've had this PC I've had turbo boost off. With it on (and at all default settings) I don't see _any_ change in temperature.. so.. I'm just wondering..


-How does turbo boost work, exactly? 
-Are there any pros/cons for using it, or for not using it?
-Why does changing the multiplier do nothing?
-What purpose is there to disabling cores?


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## greenbrucelee

*Re: Turbo Boost... How does it work?*

Basically turbo boost makes the cpu work past its rated clock speed. It only activates when the OS needs the best cpu performance possible.

For sandybridge cpu's it will auto clock itself in increments of 100MHz but Auto or turbo boost is dependant on electrical and thermal limits.

so for example you could get to 3.7 or 3.9 with turbo boost but as the heat rises turbo boost will drop the multiplier this may happen so fast that cpu-z or any other monitoring app does not even detect.


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## Wrench97

*Re: Turbo Boost... How does it work?*

The number of active cores comes into play also, if you run a video editor capable of multi-threading for example the speed will be limited as all the cores are being used.


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## cl-scott

*Re: Turbo Boost... How does it work?*

So just to kind of put everything together into a single post...

Turbo Boost does allow the CPU to dynamically overclock individual cores on the CPU based on need and thermal constraints. The more cores are active, the less the CPU will allow any given core to be overclocked. If only one core is active, you might have a CPU that can overclock rather significantly, and if more than one core is active, it will only be able to go up a little bit. 

Turbo Boost can be thought of like a cap and trade sort of system. The CPU, and we'll assume a dual core for the sake of the example, is designed to withstand both cores operating at full speed for sustained periods of time, so that would be the cap. Now, if one core is inactive, for whatever reason, it can "trade" its share of the cap to the active core, so it can ramp up the speed. If the second core becomes active, the first one is scaled back so that the total CPU cap on heat is not exceeded.

So there are really only up sides to using turbo boost. It can speed up tasks, and since the hardware keeps the heat in check by dynamically scaling the overclocking rate, there's basically no down side.


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## Wrench97

*Re: Turbo Boost... How does it work?*

Yes, that is done automatically, there nothing stopping the CPU from being overclocked manually in the bios the old fashioned way.


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## greenbrucelee

*Re: Turbo Boost... How does it work?*

Overclocking manually gets better results and instead of turbo boost working to what the manufacturer says is acceptable levels. Overclocking manually can be done within your own paramaters.

Obviousley overclocking manually can go wrong and does void warranties but the most I have seen turbo boost do is 3.9 but with the i2500k as noted in my guide is possible to clock it to 4.5 with ease and with the correct setup 5GHz can be got to easily, getting to 5.2 is pushing it though.


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## wkw427

*Re: Turbo Boost... How does it work?*

Hmm. I think I understand. I'm going to try to bump my clock up to 4 this weekend. Just to see if I can do it.
Thanks


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## greenbrucelee

*Re: Turbo Boost... How does it work?*

Just follow my guide for the i2500k 4GHz is no problem neither is 4.5.


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## wkw427

*Re: Turbo Boost... How does it work?*

Yeah, only thing that kept me away from OCing was the variations in setting names board manufacturers have.


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## greenbrucelee

*Re: Turbo Boost... How does it work?*

If there is a term that is different for your BIOS PM me.

When I did that guide it was based on an Asus board, so all the terms should be the same.


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## Tyree

*Re: Turbo Boost... How does it work?*

@wkw427
If you are using the PSU listed in your "My System" you should be cautious with the OC.


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## wkw427

*Re: Turbo Boost... How does it work?*

Alright. I'll keep that in mind on the weekend


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## greenbrucelee

*Re: Turbo Boost... How does it work?*

Yeah never noticed you were using a GS series you will be ok with turbo boost but if any vcore changes are needed with a manual overclock then you may run into issues.


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## wkw427

*Re: Turbo Boost... How does it work?*

Well aware of that. Might think I buy a new seasonic, too. Current one has EMI making my front panel audio headers useless. 
Going to get a modular one, too.


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## greenbrucelee

*Re: Turbo Boost... How does it work?*

the seasonic x series are the best out there at the moment. They are 88% (upwards) efficient.


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## Tyree

*Re: Turbo Boost... How does it work?*

All SeaSonic- All XFX- Most Corsair (not the CX-GS-M Series) are top quality.


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## wkw427

*Re: Turbo Boost... How does it work?*

Yeah, no matter what I try, I can't change the multiplier as shown in the bio from anything other then 16x and 33x :\


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## greenbrucelee

*Re: Turbo Boost... How does it work?*

when you enter the BIOS you need to change the bit that says all cores to 4 and any auto overclocking options to manual.

You should be able to type the multiplier in as 40 (assuming you are using a board with a UEFI bios.


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## wkw427

*Re: Turbo Boost... How does it work?*

Did some tweaking, with a 40x multiplier, Windows now reads it as 3.30ghz, 3.90ghz. Intel turbo boost monitor reads it as 3.47 ghz, and cpuz shows it maxing at 3458mhz, with a 33x multiplier..


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## greenbrucelee

you need to knock off any intel speedstep or c1e settings off too, you can re-enable them after a succesuflt overclock if you want power saving.


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## cyricc

I believe what Tyree said about your PSU is correct. 

Take a look at: http://www.kitguru.net/components/cpu/zardon/power-consumption-fx-8150-v-i5-2500k-v-i7-2600k/

If you notice, the 95w TDP is the maximum power consumption under STOCK clocks, when you overclock, power consumption starts to rise. At 3.3 you are looking at ~128w consumption, at 4.6 its 206w and the 5ghz mark is looking much higher, if you couple that with your video card, which requirements at stock clocks is 450w, you start reaching your 600w limit, and as we know 88% efficiency means you are only guaranteed to pull 528w to your system.

In regards to Turbo boost, you pretty much have all the info correct. It's a dynamic monitoring program that changes clock, power, and processor usage based on demand. The default settings is for 3.3 but when you over clock you are adjusting this setting to higher levels. Turning Speed Step ( the name for downclocking, where Turbo Boost is the name for overclocking) off, keeps your cpu at the set clock rate, stock or whatever you set the multiplier and blck to.


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## wkw427

Time to.. not attempt to overclock in that case!


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