Purpose to Throttle CPU?

Hi,

What is the purpose of throttling the CPU? I am using RMClock. I understand what it means to undervolt... it saves battery power by reducing voltage consumption at each CPU step.

However what is the purpose of throttling the CPU when the voltage consumption is still identical at each CPU step? While throttling, I find my laptop at 100% CPU power more frequently, which is equivalent to the maximum voltage consumption regardless of throttling!

 

Hi jjohan,

I am not sure that I understood your question. You got that undervolting part right. When you say throttling, do you mean changing the steps (multipliers) depending on usage?

I may be off the subject, but anyway this may help you:
The point of changing the multipliers is the change of the frequency of the CPU (FSB x multiplier = CPU freq), and voltage per step is different (lower multiplier = lower voltage, not the same as you said). So default multipliers and their change depending on load is OK - I don't see much point of changing WHEN (at what load) will CPU change its multiplier. Although that is possible and easy (at least in NHC) - there is no big difference in power consuption. Also there is no point in changing what will be the highest multiplier (or lowest), because either you need 100% or lowest possible (on idle). I would really like to know why someone would change this (any ideas?).

The whole point of saving power (and keeping your notebook cool) is undervolting - you don't play with multipliers, percentages of load when to change, nor limit the multipliers to your liking. You just lower each step by 0,2V for example and enjoy a new cooler notebook. Meaning for example when the Pentium M 750 CPU is on idle instead of 0,988V it uses 0,732V and when gaming instead of 1,3V it uses 1,1V - making it much cooler.

I am not so familiar with RM clock (I use NHC), so I might have missed something in your question.

Ivan

 

are you talking about intel's Speedstep, amd's PowerNow!, etc.? the purpose of CPU clock throttling is simply to reduce power consumption, which in turn reduce heat dissipation, which reduce noise because the fan don't need to turn on very often - well... you get the picture.

 

Not sure if this answers your question, but a CPU 100% loaded @800MHz still consumes less than 50% @ 1600Mhz, as dynamic losses are higher. There's always a 'base' consumption, not connected to load, and that's just lower at lower frequencies. On top of that, lowering frequencies also allows for lower core voltages, in turn good for a nice power bonus.

 

i think ice-tea is the only one who sorta understands what i'm asking about. NHC also lets throttling. its in the bottom right corner on one of the windows, where you can change 100% to whatever percentage you like.

i understand that 100% @ 800 Mhz will consume less power than 50% @ 1600Mhz (to get this, you are throttling at 50% in NHC or RMclock). However if you look at your settings, regardless of how much you throttle, the CPU is still at the original maximum multiplied speedstep.

 

and voltage consumption is dependent on the multiplied speedstep, not CPU frequency...

 

Power = Current * Voltage
With the voltage held constant, reducing clock speed will reduce the current draw and reduce power consumption.

 

That NHC 2.0 throttling option ('CPU Modulation') works by inserting no-ops so the CPU can spend more time in deeper sleep states.

It is a software thing, unrelated to SpeedStep/PowerNow or undervolting.

I haven't found any use for it, although in theory you could use it to get effective speeds below the slowest SpeedStep.

 

Jumper - you are right - I knew I was missing something. Thanks for reminding me! I completely forgot about CPU modulation. I must give it a try, and test it on battery.

Thanks,

Ivan