Does Turbo Boost really matter?

[Krane]

All the new Intel CPUs flaunt it. But does it really do much? How does it work? How does it relate to real world operating results? How and when does it get applied? Who sets the parameters for its operation?

I know Adobe products can take advantage of multi-core/multi-threading, but do these turbo boost "afterburners" really add anything?

[tijo]

I can't say i tried disabling it for real world usage to see how much it matters. However, it does indeed work as advertised when i run single threaded benchmarks, it rarely turbos to full because of either tdp or windows scheduling the other tasks to another core.

It does work if you send heavy work to one or two threads though, the clock speeds will indeed increase to process the task faster. How much does that translate in real world time, i'm not really certain. I can see having benefits for single and dual threaded workloads, but on 3 threads or more, the difference won't probably be noticeable unless you run a multithreaded intensive task that can take a while.

As for how TB works, i can't really say in details for SNB, but for clarksfield, it will "put the unused cores to sleep" (power gating iirc) and then increase the clock speeds on the active ones up to the max specified turbo or until it hits the CPU's TDP. The increase in clock speed will depend on how many cores are used and how much they are used. I know this is a somewhat shallow explanation, but it is the best i could gather so far from testing with my 920xm.

I can post screenshots of throttlestop reporting the clock speeds while running wprime on 1, 2, 4 and 8 threads if you'd like.

[jotm]

In my experience, most people won't notice the 1 or 2 core TurboBoost at all, no matter what apps they're using, unless they're using a pre-Windows XP operating system.

The reason is that the OS itself is very good at spreading the load of any application (single-, double-, triple- or whatever threaded - doesn't matter) over all of the existing cores.

TurboBoost just increases the frequency for one or two cores so that the OS doesn't have to spread the load, saving a couple of milliseconds at most, which is unnoticeable in everyday use (though good for benchmarks if every tenth of a second counts).

However, if you're fully loading all 4 cores, there will be a slight (but noticeable) difference in performance even if only one or two cores are using TB, because when you need all the performance your CPU can provide, every extra MHz counts.

TurboBoost on all cores is obviously useful for the same reason, but you'll only get it if your laptop has a good cooling system...

[baiii]

throttlestop and be always turbo boosted?

[Cloudfire]

[Meaker]

On mobile CPUs with large turbo boost ranges? A large difference.

[Dufus]

Originally Posted by Krane

But does it really do much?

It can increase the speed at which the CPU runs.

Originally Posted by Krane

How does it work?

Depends how it is set up but traditionally if some cores are not doing much then more power can be delivered to the other cores enabling them to run faster while keeping the package within it's TDP specification.

Originally Posted by Krane

How does it relate to real world operating results?

Usually the faster a cpu runs the quicker it can finish a task.

Originally Posted by Krane

How and when does it get applied?

See above.

Originally Posted by Krane

Who sets the parameters for its operation?

Intel. Although some configurable parameters may be available to the end user.

Originally Posted by Krane

I know Adobe products can take advantage of multi-core/multi-threading, but do these turbo boost "afterburners" really add anything?

Usually the faster a cpu runs the quicker it can finish a task.

[davepermen]

it matters where you notice it most: for the quick speed when needed. imagine decoding a movie or something. there might be a short moment, where you'd have a cpu spike resulting in too low of a performance to decode it in realtime. if the cpu is capable of overclocking at that short moment, you won't notice a stutter, or audio dropout, or similar.

so when ever there would be that short moment where your system feels non-smooth, turbo boost can help to smoothen it out by quickly boosting it for a short moment.

i have a 1.6ghz core i5 samsung tablet. it's a very slow cpu, theoretically. but you'll never notice, as it always, on peaks (like scrolling in a browser, starting an app, loading and analyzing tracks while playing others (i'm a dj)) boosts to 2.3ghz or so, as needed.

it, essentially, fixes all the moments where the system can't correctly multithread, as a single thing running gets stuck and cries for more performance.

for me, the impact is very feelable, similar to what an ssd does. it fixes the typical snappiness-bottlenecks.

[lidowxx]

Originally Posted by Meaker

On mobile CPUs with large turbo boost ranges? A large difference.

Very true, mobile CPUs have MUCH more aggressive turbo ratio than the desktop CPUs.

My 2630qm sits tightly at 2.6ghz when all 4 cores are stressed, that's 30% faster than the stock 2.0ghz. Whenever I am doing video encoding and 3d rendering, it makes a BIG difference, you won't notice the speed boost during normal use though.

Of course, the turbo boost depends largely on the cooling system, I have seen plenty of people can't maintain their SB CPUs at intel's advertised speed when they are under load simply because of inadequate cooling.

[Dufus]

Originally Posted by lidowxx

mobile CPUs have MUCH more aggressive turbo ratio than the desktop CPUs.

Not so sure about that.

My desktop SNB CPU turbo's from 33x to 50x, others have been up to 59x. An older i7-860 was 21x to 26x and I even had a i5-655k that could turbo from 24x to 99x (75 turbo bins) although that was just done to see how many bins could actually be used.

Even the locked SNB desktop chips can support an additional 4 bins with the right setup, for instance i5-2400 31x to 38x.