Noob turbo question

I'm confused by turbo on intel processors, if the turbo speed is the maximum clock speed that it can reach, then why not say that is it's clock speed and throttle when the demand is not up to it? Or is it just another marketing phrase?

 

because from what i have heard that turbo only comes on when its not using all of its cores

 

Wrong. There's turbo boost for all cores, or only two cores etc. But the amount of the turbo boost (by default) higher for one core than for several cores.

You only get Turbo Boost as long as your system is still withing the defined thermal envelope and only if there's enough load.

For example an i7 720QM runs at a clock speed of 1.6GHz, that's what you get when there's enough load, 1.6GHz on all cores. (Unless the system is poorly designed and throttles itself)
Now if there's enough thermal headroom, the CPU can use Turbo Boost and adjust the speed. On a 720QM the max turbo frequency is 2.8GHz, but that's only for one core in use.
For four cores for example the Turbo Boost will it only push to about 1.7GHz (maximum).
So the standard multiplier of a 720QM is 12 (12*133MHz is about 1.6GHz).
The max turbo multi for 1 active core is 21 which results in about 2.8GHz.
Etc., the more cores active, the lower is the max turbo multiplier, and you only get Turbo Boost as long as the CPU doesn't run too hot. Otherwise it will lower the Turbo multi or even go back to 1.6GHz.

Edit:
Found it... the max turbo multi for an i7 720QM:
4 cores: 13 - 1.7GHz
3 cores: 13 - 1.7GHz
2 cores: 18 - 2.4GHz
1 core: 21 - 2.8GHz

 

The turbo multipliers are different depending on the number of cores used.

Here are the specs for my 920xm:

Base multiplier: 15, BCLK 133MHz
4 core turbo: 2 -> 17x0.133 = 2.2GHz
3 core turbo: 2 -> 17x0.133 = 2.2GHz
2 core turbo: 8 -> 23x0.133 = 3.05GHz
1 core turbo: 9 -> 14x0.133 = 3.2GHz

It's possible the CPU will run at it's base multiplier if power consumption goes too high.

Dang, ninja'ed by Svl7 by less than 1 min .

EDIT: The 720qm can actually run at x13 on 4 cores in most cases. I've only seen it run at x12 on prime95 when i had one in my G73.

 

Because it is not guaranteed to run at that clock speed. For example, the 2720QM is guaranteed to run at 2.2GHz unless there is a hardware fault. However, if you load up all 4 cores and have a good cooling system, it may run as high as 3.0GHz with Turbo Boost. In practice, it stabilizes around 2.4-2.6GHz with most cooling systems and all 4 cores loaded, but the guaranteed speed is 2.2GHz.

 

But even so, at all cores usage, it's not guaranteed to run at the rated speed though. For example, my i7-2630QM is rated at 2 GHz when all cores are used, but if my temperatures are very very very high, it will downclock below that.

 

But that's simply due to a poor cooling design. A CPU should be able to work at its rated speed, and the cooling system should be able to handle this.

Maybe it would help if you repaste your CPU and make sure that the vents are free from dust.

 

This is what I meant by "hardware fault". All modern CPUs (Turbo or no Turbo) will downclock rather than fry, but that should never happen unless there is something wrong with the system. Turbo Boost is special in that it will try to work outside of design operating parameters, but is not guaranteed to do so given various environmental factors.

 

That's not a fault, not at all. Otherwise thousands of dusty systems would kill their CPU. Keep in mind that most users don't repaste or not even clean their system once in a while...

The manufacturers that build systems with insufficient cooling systems should be blamed, not the CPU manufacturers which include safety mechanisms to prevent your precious CPU from frying itself.

 

That, a good cooling design should always include some headroom for hot days. Unfortunately, some laptops (only a few) have CPUs with a TDP too high for their designed cooling. I'm not talking about gaming laptop cooling type of headroom either, but just a little bit so you won't ever have to go into thermal throttling unless the system is clogged up with dust.

 

The downclocking is not the fault, its design. In your example, the fault lies with dust in the hardware.

 

just so we are clear i'm not saying my cpu runs below the rated speed, i'm just saying that would be the behaviour if it got too hot

 

this works for all cpus, not only this new iteration

 

I know, I was just stating that it is odd that the rated speed is 2.0 when clearly it can go above/below that.

 

The rated speed is guaranteed at the CPU's TDP. The turbo will work as long as it doesn't exceed the TDP over long period of times or gets over Tj which is 100C for core i's. If it gets over the TDP, it will fall back to it's non turbo rated speed. As long as my 720qm didn't exceed 45W, it would run at x13 (4 cores) multiplier. Some programs like prime 95 pushed the TDP higher than 45W at x13 so it went back to x12 which is the rated 16GHz multiplier under those circumstances. There's no way thermal throttling was kicking in either on prime95. The max temp i ever got was ~75C.

 

this is what I have to say about turbo boost