What on earth is the point of "CPU Throttling"?

redarrow

redarrow

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Just wondering...

I always assumed that CPU throttling was some kind of "power saving mode" ... but now I've heard that it doesn't actually slow the CPU down, it just forces it to sleep for a certain percentage of "cycles" ...
In this case I find it hard to believe that it could save much power... :confused:

So whats it really for? :confused:
CPU cooling mode or something like that?
 
redarrow said:
Just wondering...

I always assumed that CPU throttling was some kind of "power saving mode" ... but now I've heard that it doesn't actually slow the CPU down, it just forces it to sleep for a certain percentage of "cycles" ...
In this case I find it hard to believe that it could save much power... :confused:

So whats it really for? :confused:
CPU cooling mode or something like that?
Click to expand...

I'm not sure about the details, I'm sure that the CPU does actually slow down. My notebook is a 1.8GHz which runs at 800MHz most of the time, except when I do heavy stuff.

If I compare doing CPU intensive stuff to typing e-mail etc. (CPU sitting at 800MHz), the two differences are battery life (almost doubles), and heat. When it runs slower, it runs cooler, the fans turn slower, you use less power, there's less noise, the fans will last longer, etc.
 
On the Intel Prescotts-based Pentium 4's Thermal Throttling was used cause these things used to run too hot too easy. That is what you decribed, the CPU was forced to sleep some cycles too keep the processor cool enough in situations where it was running too hot.

AMDs Cool & Quiet and Intels SpeedStep (used on mobile Pentiums and not mobile Celerons) actually makes your CPU run slower, for example my moms A64 2800+ runs at 1GHz and 1.1V instead of 1,8GHz and 1.5V most of the time...
 
koffiejunkie said:
I'm not sure about the details, I'm sure that the CPU does actually slow down. My notebook is a 1.8GHz which runs at 800MHz most of the time, except when I do heavy stuff.

If I compare doing CPU intensive stuff to typing e-mail etc. (CPU sitting at 800MHz), the two differences are battery life (almost doubles), and heat. When it runs slower, it runs cooler, the fans turn slower, you use less power, there's less noise, the fans will last longer, etc.
Click to expand...
The thing is I don't notice any difference apart from a slowdown on my laptop :confused:

If I set it to the maximum throttle state it becomes very slow .. but I don't get any improvement on battery life.. :confused: - at least nothing noticable...
 
redarrow said:
The thing is I don't notice any difference apart from a slowdown on my laptop :confused:

If I set it to the maximum throttle state it becomes very slow .. but I don't get any improvement on battery life.. :confused: - at least nothing noticable...
Click to expand...

What processor does your laptop have?
 
supersunbird said:
On the Intel Prescotts-based Pentium 4's Thermal Throttling was used cause these things used to run too hot too easy. That is what you decribed, the CPU was forced to sleep some cycles too keep the processor cool enough in situations where it was running too hot.

AMDs Cool & Quiet and Intels SpeedStep (used on mobile Pentiums and not mobile Celerons) actually makes your CPU run slower, for example my moms A64 2800+ runs at 1GHz and 1.1V instead of 1,8GHz and 1.5V most of the time...
Click to expand...

hmm guess that explains it...
I have a Celeron laptop (Acer Aspire 3613) so I guess it must have that cycle sleep thing...

Thanks for the explanation.. ;)
 
redarrow said:
Intel Celeron M 370 1.5GHz
Click to expand...


I don't know about CPU frequency scaling, but I know for sure the Celeron-M doesn't have the Centrino power saving features that the Pentium-M has, where certain parts of the chip will be switched off when not in used.

I would guess that CPU throttling and frequency scaling are two different things then. If throttling is in fact the sleeping cycles thingy, then that would explain why you get a performance reduction, but no improved battery life. It should keep it a little cooler though (although the Celeron-M and Pentium-M chips don't run too hot to start with, especially not at 1.5GHz).

Speaking of which, I made a bizarre observation on my old notebook, Compaq Armada m700. It was a 1GHz Pentium 3 (*not* a Mobile Pentium 3 though). At the time I had a 1GHz P3 desktop at work, and the two chips had the same family, model and stepping numbers. In fact, they were identical down to the revision numbers. I ran Debian Etch on it, and the weird thing was, out of the box, without any fiddling from my side, I had CPU Frequency Scaling - the chip went right down to about 300MHz at times.

I got it with a dead battery, and bought a 3rd party replacement (from a chinese shop in Edenvale). Gave me about 5:30h battery life....
 
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