How long can a CPU stay on Turbo Boost?

[b2013]

Hi everyone

Intel claims on its website that with Turbo Boost, a CPU can raise its clock frequency "when necessary", under some temperature constraints.

I'm a Software Engineering student and I work with programs like Matlab, which does calculations that sometimes take 1-2 minutes. So I'll need high performance.

I'm going to get a Macbook Air with this CPU, which turbo-boosts from 1.7 to 3.3 GHz.

My questions is: will my macbook be able to stay on Turbo Boost for 1-2 mins - or it will return back to normal mode earlier than that?

It would be extremely nice if you helped me with this question.

 

[ldewitt]

Turbo boost AUTOMATICALLY Accelerates your CPU as needed, so theres no really time frame that it will be in "Turbo Boost" It just takes it as needed and when it doesn't need it anymore turns off to conserve power and/or to cool your cpu down if it starts getting to hot.

 

[Unolocogringo]

That all depends on the cooling. Keep it cool and it will stay in turbo mode.
As far as Air goes , not very long. Their cooling solution is not good enough to keep it in turbo mode. They are designed for style not performance.

 

[nukemaster]

On top of power and thermal limits. Turbo also looks at the number of active cores. With less cores in use, you can increase the speed of the working cores with the extra power the idle cores are not using.

This will depend on many factors. and Unless someone has the same system test of, It is hard to give you a 100% answer.

Seeing as you have a dual core cpu. I would have to guess that top end boost clocks are not always going to happen. The harder the workload. The lower the clock speed will end up.

This does not make the cpu a bad one. It is just the way they work

 

[thasan1]

it will be able to stay in the boost mode for 1-2 minutes if the CPU is cool. if the CPU starts to overheat it will go back to 1.7Ghz to cool it down.

 

[b2013]

Thanks a lot guys for the answers.

I know maybe it's hard to give a precise answer, but how is it approximately? I mean, when they say Turbo Boost, do they mean just like 20-30 sec - or it can actually stay for a few minutes?

...The harder the workload. The lower the clock speed will end up.

Do you mean it will end up with a lower clock speed after having done the work - or while doing it?

 

[nukemaster]

The clock rate would drop while doing hard work.

It will NOT drop below 1.7ghz under almost any circumstances(it has to overheat for it to drop any lower than that).

It is hard to give you an exact time it will stay boosted because all chips are a bit different and so many other factors come into play.

Takes too much power. clocks down a bit(some chips simply take less power than others.)
Gets too hot. clocks down a bit. This can be vastly effected by the cooler in the notebook and even its hardware setup.
loads all cores(100%), clocks down a bit

 

[Unolocogringo]

From a cold boot you would get full turbo boost for a couple minutes.
After the laptop has been used for a while it is already warm, so the turbo boost time would be much less.
If your program uses 2 cores it would not boost to 3.3 if both cores are @ 100% usage for any length of time.
Matlab is multicore capable ,depending on the simulation you are running. If your simulation uses both cores ,turboboost will be lmited. It may not ever run a 3.3 on both cores while running your simulation.

There are way to many variables to give an exact answer. But generally do not exxpect 3.3 on both cores for you simulation runs.
Part due to the design of turbo core and part by the design of the Air. Its cooling capabilities are not the same as a full size laptop, where larger heatsinks and fans can be used.

 

[b2013]

Ok thanks for the explanations.

My alternative choice is Macbook Pro late 2013 (2.4GHz dual-core Intel Core i5, Turbo Boost to 2.9GHz), which scores weaker or similar to the core-i7 Air in benchmarks.

How come this happens? I mean, if Turbo Boost is "much less than 2 mins" if the system is already warmed up, and max clock frequency cannot apply to both cores simultaneously, then how come the Pro's CPU, with a higher base frequency, scores worse/equal?

 

[Unolocogringo]

Newer processsor design. With an emphasis on power management.
About 7 to 15 % improvement per clock and depending on programs use of hyperthreading.
The older Core I 5 may be 2 core 2 threads , the new I7 is 2 core 4 threads.
4 threads @1.7 is slighty faster than 2 threads@2.9 and a good bit faster than 2 threads @2.4. in well threaded applications. Matlab is well threaded depending on your simulation so it could use 4 threads.

 

[b2013]

Thanks. Actually they both have 4 threads.

So can we say the Air's CPU performs faster than the Pro's CPU?

 

[Unolocogringo]

Theoretically yes.
If both were in the same laptop, definitely, as they would have the same cooling.

The I7 has a TDP of 15watts and the I5 28watts, or almost twice the heat that needs to be dissipated.
If the air can keep the I7 cool it will always win, If not it will throttle down from overheating. That is why they swap leads in the benchmarks you talked about in an earlier post.

If the simulations that you will be running are only a couple minutes the Air would win.
If they take 10 minutes or more the Pro would probably win.
The better cooling of the pro would keep the processor boosted at a higher frequency for longer.


I understand that the Air is a much better looking laptop, and you are trying to justify buying it over the pro. Which in my opinion is "MEEHHH" as far as looks.

The temperature of the CPU will determine the speed the CPU runs at.

For serious work get the pro. If your simulations are only a few minutes they are about even,slightly leaning toward the Air.

 

[b2013]

Actually the reason I'm more interested in the air is its lightness, as I'll have to bring it to the school everyday. )

My simulations will rarely take more than 2 minutes.

From what you say I understand that in short-time simulations (2 minutes) the air wins as it overclocks to a higher clock speed (3.3 vs. the pro's 2.9), and it's i7.

Am I right?

 

[Unolocogringo]

Yes . the Air's higher clock speed will win for short simulations,

 

[b2013]

Ok.

Thank you so much - and also thanks a lot to all those who helped me with my questions.