Drastically underclocking CPU/GPU when idle

[neosapien]

I've got a Core 2 Quad 6600 B3 @ 3.0Ghz, 1.30V. I'm interested in underclocking it when it's idle, to around 1.6Ghz, 0.85V (or 1.2Ghz or whatever it would be stable at at 0.85V). The reason I am interested in this is the potential power savings that would result, though I'm not sure how many watts the cpu would consume at idle 3.0Ghz 1.30V vs 1.2-1.6Ghz 0.85V. Intel Speedstep is simply inadequate, all it does on my computer is reduce the clock speed from 3.0Ghz to 2.0Ghz, it doesn't even adjust the voltage. So, are there any applications that can facilitate this? Run the CPU at 1.2Ghz-1.6Ghz 0.85V, and automatically switch to 3.0Ghz, 1.30V when the CPU is no longer idle?

I'm also interested in underclocking my Geforce 8800GT when it's idle. Right now, I can do this somewhat through RivaTuner, by telling it to reduce the core/shader/memory clocks by half when hardware acceleration = 0, but I wonder if there is a better way. I've vaguely heard of people being able to edit the BIOS so that the GPU runs at a lower voltage and lower clockspeed in 2D mode, and then at standard settings at 3D mode, but other people have also said that the 8800GT can't switch speed and voltage settings between 2D and 3D mode. Can someone shed some light on this, and explain how to do this, if indeed it's possible?

 

[Tempered81]

Rmclock

 

[neosapien]

When I go into rmclock's Profiles, I see an option to edit the CPU Performance States, but the multiplier is only adjustable between 6x-9x and the VID will only go as low as 1.1625V (and as high as 1.325V), whereas I'd be looking for a way to get the multiplier down to 4-5x, and the VID down to 0.85V.

 

[SolMiester]

Probably because it wont run at such a low VID......do you turn your PC off or leave it going continuously?....I wonder how much power you hope to save?...

 

[neosapien]

I turn my PC off at night. I'm not exactly sure how much power it would save, going from 3.00Ghz @ 1.3V idle to around 1.2Ghz-1.6Ghz @ 0.85V. Going by this page, which has Q6600-B3 standby consumption at 38 watts, and 1x prime consumption at 64 watts, I suppose 3.00Ghz @ 1.3V idle would be around 50 watts or so? I don't know any exact figures, but maybe 1.20Ghz @ 0.85V would consume something like 21.6055535 watts or so?

So Q6600s won't run at 0.85V, given a low enough clock speed? I assumed that since it's in the Intel specs as 0.85V-1.5V, it was just a matter of clock speed.

 

[Binky]

The multipliers are fixed by the factory. RMclock only allows you to manipulate what is already there.

For the voltage, RMclock only shows the voltages it thinks are there. If you run at stock voltage, these should be approimately correct. If you undervot the CPU in bios, then the RMclock voltages shown will be higher than actual for each VID. For example, if your base voltage is 10% less than stock, then RMclock will show VID voltages that are ~10% too high. I hope I'm making sense. It's been a while since I've tinkered with RMclock and I'm a bit rusty on the terminology.

If you never need the top speed on that machine, you can lock out the top multiplier (in RMclock) and undervolt it in bios. Then tune in windows with RMClock as you please.

Try silentpc review forums for extreme undervolting advice. Some MB's are better than others for this.

 

[Idontcare]

Originally posted by: neosapien
So Q6600s won't run at 0.85V, given a low enough clock speed? I assumed that since it's in the Intel specs as 0.85V-1.5V, it was just a matter of clock speed.

Oh it'll run that low but you have to also adjust your FSB down to 800MHz (200MHz quad-pumped) and reduce your CPU multi to 6x.

But yes, the 6x multi is the lowest any Core-based product can go, it doesn't possess the hardware to recognize any lower clock multipliers.

My recommendation is to setup your OS to put your computer into sleep mode (not hibernate, just sleep) if it is idle for 5 minutes or something of that nature. A lot simpler and you'll save more wattage over time versus running the computer for an hour at a time at idle but low GHz.

 

[GundamF91]

I like RMclock, but it does not support 45nm, and they've stopped developing it. I used to run it on Conroe, and you can set up your VID floor so you undervolt it.

To this date, I still don't know why Intel Speedstep does not lower voltage as it lowers multiplier. It's built in there, but Intel doesn't use it.

 

[Idontcare]

Originally posted by: GundamF91
To this date, I still don't know why Intel Speedstep does not lower voltage as it lowers multiplier. It's built in there, but Intel doesn't use it.

But...it...does...?

What are you talking about/looking at?

My quads drop to 1.1V (and lower) at idle from 1.35V at load while the multiplier drops from 9x (or 10x) to 6x.

 

[GundamF91]

Does the vCore change along with multiplier?? I use CPU-z to monitor my vCore, and all I notice are Multiplier drop, ie. 8x to 6x, but the vCore stays the same everytime.

I wonder if you have your vCore in BIOS set on "AUTO"? I wonder if that makes the difference. I have mine set at a certain value and not on AUTO. It could be that vCore is only adjustable by Intel driver when it's set on AUTO. When the system is overclocked and vCore hard set at a value, then it is fixed in BIOS, and the Intel driver won't make the VID go up or down. On the other hand, I know RMclock was able to adjust the VID even if you hard set a vCore value in BIOS, so maybe RMclock overwrites the setting.

 

[katank]

@OP, not worth it. You save a negligible amount of power at idle by undervolting.

If it was really idle, why don't you either put it into sleep mode or hibernate the machine? That'd be far more effective in saving power.

If it's not really idle, then you can let it run. It'll probly cost you a couple of bucks a year at most.

 

[Idontcare]

Originally posted by: GundamF91
Does the vCore change along with multiplier??

Yes it does. This is how C1E and EIST work when they are working.

Originally posted by: GundamF91
I wonder if you have your vCore in BIOS set on "AUTO"? I wonder if that makes the difference. I have mine set at a certain value and not on AUTO.

Ah, that is why. Setting the Vcore manually results in disabling the voltage-reduction features of C1E/EIST.