Idle consumption seems high, any ideas?

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flyingsherpa
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Idle consumption seems high, any ideas?

Post by flyingsherpa » Fri Sep 17, 2010 5:50 am

So I built this system (part list there and in my sig) a while ago and it's working out great, but I'm kind of disappointed in the power consumption. I pay about $0.24 / kWhr here so I purposely chose the mobo, cpu, and psu so I'd have an uber-low idle consumption, but it generally idles at 44W (Kill-a-watt, from the wall). Way above what I thought I'd get. I see a lot of builds with i3's or other AMD e-series CPUs that claim 20-30W idles. I see in my linked write-up that I claimed a 30W idle at one point, so I must have seen that on the kill-a-watt before (or maybe it was wishful thinking), but not recently... though very rarely I see it go to 33W for a second. I looked up the p-states for the 240e and the 44W idle corresponds to the lowest p-state values when checked with CPU-Z.

The only expansion card in there is a HVR-2250 tv tuner and I've measured that it only changes the idle numbers by a watt or two if I remove it. I do have three 120mm fans hooked up to two fanmates (all set to 600rpm or lower)... I have not tried unplugging those, maybe fanmates are really inefficient? Or maybe my super special Dell RM112 Gold is not all its cracked up to be...

Anyone have ideas as to where I'm gaining 10-15W at idle?

maalitehdas
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Post by maalitehdas » Fri Sep 17, 2010 9:22 am

Your PSU (235W) runs at about 80%-85% efficiency with low load of 44W. That lives your PC 0,85*44W=37W (7 watts of 10-15 solved?) or
That lives your PC 0,80*44W=35W (9 watts of 10-15 solved?)

Tuner card gives ~1W, each fan adds another ~1W. (11-14W solved?)

If you have any extra performace in your CPU (check usage level while doing your most demanding jobs), there might be a possibility to undervolt it. I did it from 1,125V to 0,8V and power consumption of CPU dropped from 35W to 12W (at 100% CPU stress test, approximate readings).

BillyBuerger
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Post by BillyBuerger » Fri Sep 17, 2010 4:28 pm

My experiences with an AII 245 undervolted was that it was hard to break 40W idle. This was with a gigabyte board that was probably not the most efficient though. The fact that it has an 8-pin CPU power hints at being designed for the more power hungry CPUs. But I would still expect mid 30s idle for a bare-bones AM3 system. That being CPU, motherboard, memory and a laptop or SSD drive. Add in the extra power for the 3.5" drive the tuner and 44W sounds about what I would expect for that setup.

One thing to check, is C1E enabled on your motherboard? It wasn't on my board at first. Enabling that allows the CPU to go into a deeper sleep when there's nothing going on which can easily drop it at least a few watts. Maybe that's where you've seen it drop occasionally. But C1E is different from the p-states. It will be at the lowest p-state when idle whether it's in C1E or not. C1E just shuts down some more parts of the CPU. Maybe something in the background is keeping it from going into C1E or at least not letting it stay there for more than a moment.

And maalitehdas makes a good point about undervolting. You do have a e series CPU but there is usually still some room for undervolting. Which might help shave a few more watts. My AII 245 (no e) was able to do -0.2V for a range of 0.8 - 1.15V... Actually, I might have to check that. I think I may be doing a BIOS undervolt of -0.1V but then use K10Stat to bring the voltage down a little more. I think there was more room on the idle side than the load side. Maybe 0.75 - 1.2V or something.

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Post by loimlo » Sat Sep 18, 2010 9:09 am

Try to undervolt your CPU to 1G @ 0.8V or even lower depending on your luck. You should be able to squeeze 3~5W compared to default CNQ 1G @ 1V.

lm
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Post by lm » Sat Sep 18, 2010 12:50 pm

(0.24 (US$ / kWh)) * 15 (W * year) = 31.5 U.S. dollars a year for 15W extra. But I doubt you can actually save that 15W in your current system without investing much more money and so it won't pay off.

One thing to try is to disconnect everything that is not essential to boot the system to find out your bottom consumption level. That means keeping just the system drive and one stick of memory, then disconnecting all fans for the duration of the measurement (don't fry your system though).

Then you know that the bare essential system with just cpu, mobo, psu, system drive and one stick of RAM is what consumes that much. And then you should be able to figure out better what is the culprit.

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Post by BillyBuerger » Sat Sep 18, 2010 3:32 pm

Quick followup from my previous post. I went an plugged in the Kill-A-Watt to my HTPC. I posted about it here previously although it's out of date. The current parts are as follows...

- AMD AII 245 2.9GHz
- Gigabyte GA-MA785GMT-UD2H
- 2x2GB DDR3 1.5V (MB reports 1.6V which all my GB boards do :()
- 20GB Samsung IDE laptop drive
- Lite-On Blu-ray drive
- Antec Veris Multi-station Elite display and remote
- Antec NSK1480 w/ MT-350 80plus PSU

That's it. Pretty bare bones. Only things I could take out would be the multi-station and blu-ray drive. Idle hits 36W occasionally but is mostly 37W. That should be when in C1E. Normal idle is probably more like 40W. Although with boxee running, it seems to stick at 50W. That's better that I thought I was doing.

The laptop drive will draw less than your desktop drive. But your PSU should save you a few watts so that should be close to a wash. You have the tuner but then I have the Veris. I'm looking at your tuner as the culprit. I thought they drew more than 1W. I was testing adding parts and checking power before and the ATI TV Wonder Pro I was using at the time took my idle power from 37W to 41W AC.

maalitehdas
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Post by maalitehdas » Sun Sep 19, 2010 12:14 am

- Antec NSK1480 w/ MT-350 80plus PSU
Too powerful for your consumption? Doesn't reach 80%, could be even as low as 60-70%.

flyingsherpa
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Post by flyingsherpa » Mon Sep 20, 2010 9:13 am

BillyBuerger wrote:My experiences with an AII 245 undervolted was that it was hard to break 40W idle. <snip> Add in the extra power for the 3.5" drive the tuner and 44W sounds about what I would expect for that setup.
Ok, good to know. I just keep wondering how other people are reporting these 25W systems? Maybe they are estimating DC draw? I don't think they were doing crazy undervolting, but maybe I'm wrong.
BillyBuerger wrote: One thing to check, is C1E enabled on your motherboard? It wasn't on my board at first.
Yes, it is. I think you are right that that is what allows it to dip to 33W sometimes. Wish I knew how to make it do that more often (or really figure out what is preventing it from happening more often).
BillyBuerger wrote: And maalitehdas makes a good point about undervolting. You do have a e series CPU but there is usually still some room for undervolting. Which might help shave a few more watts. My AII 245 (no e) was able to do -0.2V for a range of 0.8 - 1.15V...
I keep meaning to try undervolting, but haven't done it yet. Need to find some time on a weekend to mess around with it. Thanks for the advice.

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