Actual difference between speedstep and turbo boost?

[Puppies04]

Bear with me on this one, I think I know what I am trying to say....

So is there any actual difference between speedstep and turbo boost on my 2500K. Yeah , yeah I know one slows the cpu down and the other speeds it up but in reality aren't they just the same thing. In the same way my 740QM in my XPS17 is a 1.73ghz cpu with a 2.93 turbo cap isn't my 2500K just a 1.6ghz cpu with a 3.7ghz turbo cap at stock?

I read about turbo only activating if the chip is working within its TDP but my understanding is that the cpu would throttle even if turbo wasn't active and I hit TJMax.

With that in mind what is the actual difference between the 2 and what am I missing?

Edit.

Also, I know turbo can make one core run faster than the others if the cpu is dealing with one heavy thread but can speedstep downclock individual cores while leaving others running at stock? Is this the difference between the 2?

 

[IntelUser2000]

It's good to remember everything revolves around the Base frequency, which is the guaranteed max frequency. For the 740QM that's 1.73GHz and for the 2500K that's 3.3GHz. Oh, and the lowest frequency for 740QM is 933MHz, vs 1.6GHz for 2500K, in LFM mode.

On the technical level, Turbo Mode is controlled by the CPU while P-states like Enhanced Intel SpeedStep is OS controlled. The base frequency is the highest P-state called P0, and every step below that using EIST goes P1, P2, etc. Turbo Mode only activates when the CPU is at P0 state, then every speed above the base clock is decided by the CPU.

Turbo Mode parameters
-Within the specified TDP and duration limit
-P0 P-state
-Full performance is demanded from the CPU

The last point is important. If full CPU isn't required, it can run at lower frequencies. On video playback, certain codecs run at the LFM frequency, which is the lowest frequency state.

But there are apps that need somewhere in between, and that's where P-states and EIST is used.

I read about turbo only activating if the chip is working within its TDP but my understanding is that the cpu would throttle even if turbo wasn't active and I hit TJMax.

TDP relates to both power and thermals. You need to be able to dissipate certain level of power. Turbo Mode requires thermal headroom to work, so if the CPU have been working a lot, you won't see Turbo active. Of course, if the CPU is throttling with no chance of a thermal headroom, then something is wrong with the design.

 

[Rvenger]

Speedstep throttles the CPU and voltage like C1E and Cstates do. Turbo justs boosts from the base frequency with is 3.3ghz on a 2500k.

 

[StrangerGuy]

The former is a mechanism and the latter is a feature that uses the former.

 

[IntelUser2000]

Also, I know turbo can make one core run faster than the others if the cpu is dealing with one heavy thread but can speedstep downclock individual cores while leaving others running at stock? Is this the difference between the 2?

No it doesn't work that way. The frequency and voltage of all active cores are the same, and its determined by the highest frequency required.

The thing with Turbo is though, when cores are disabled, you get thermal headroom. You also get thermal headroom if you are executing a low and/or idle TDP scenario so the CPU can be boosted when the performance is required, whenever. Speedstep helps lower thermals when full CPU isn't required.

As CPUs get more and more powerful, increasing amount of usage scenarios exist where applications are executed in a very short amount of time. Turbo Mode exploits the thermal headroom to boost the performance of those very short running, yet performance demanding applications.

 

[gorydetails]

i agree not use turbo for too long,,,the cpu may get burned,,,

 

[Puppies04]

Thanks inteluser2000 your consise explanation has cleared up my confusion.

Gorydetails, what the hell are you talking about

 

[Phynaz]

i agree not use turbo for too long,,,the cpu may get burned,,,

Ummm....no.

If the computer design meets the requirements as laid out by the CPU manufacturer, you are not going to damage your CPU.

 

[exar333]

Ummm....no.

If the computer design meets the requirements as laid out by the CPU manufacturer, you are not going to damage your CPU.

This.

Look at the 'K' model CPus on the Desktop. Their max single turbo is usually in the high 3.6-3.9ghz range, but folks crank up the freq for all 4 cores to 4.4ghz+ 24/7.

SB CPUs, and presumably IB too, are very 'over-built' based on stock frequencies. With the right cooling, these thinks really can fly. It should be noted that the overall life of the CPU can definitely be decreased, but the practicality of that has been debated many times here.

 

[gorydetails]

O ok,,,thx,